Add Python wrapper to ecl and use it to test functionality

* Add SWIG interface definition (and external numpy interface) to ecl classes
* Add section in CMakeLists.txt to build Python bindings and execute
  Python-based tests
* Write (property-based) tests that show the basic functionality of the Python
  bindings and the EKF (using pytest and hypothesis libraries)
* Write minimal benchmark for the EKF update (using benchmark plugin for pytest)
* Add plotting utilities to analyze tests
* Add lint script to keep the Python scripts clean

EKF/tests/pytest/ekf_test

@@ -0,0 +1,137 @@
+#!/usr/bin/env python3
+###############################################################################
+#
+# Copyright (c) 2017 Estimation and Control Library (ECL). All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name ECL nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+###############################################################################
+
+"""Tests for the ecl library (using it's Python bindings via SWIG)
+
+In order to run the tests, make sure to compile the ecl library including the
+SWIG bindings, e.g. by running
+
+    cmake -DPythonTests=1 ../EKF && make pytest-quick
+
+from your build directory.
+
+This script can also be run directly (e.g., by using `make pytest`), or you can
+run pytest on the test folder.
+
+Running the script directly provides some useful flags, in particular one can
+enable plots (using `-p`) to visualize the test results. For example, the
+following command will run all test that include the string "baro" in the test
+name and plot the results:
+
+    PYTHONPATH='/path/to/ecl' ekf_test -p "baro"
+
+
+@author: Peter Dürr <Peter.Duerr@sony.com>
+"""
+from __future__ import print_function
+from __future__ import unicode_literals
+from __future__ import division
+from __future__ import absolute_import
+
+import os
+from datetime import datetime
+import argparse
+
+import pytest
+from hypothesis import settings
+
+START_TIME = datetime.now()
+"""Record when the script was loaded
+"""
+
+# Register hypothesis profiles
+settings.register_profile("plots", settings(max_examples=0))
+settings.register_profile("quick", settings(max_examples=20))
+
+
+def main():
+    """Called when the script is run standalone
+    """
+
+    parser = argparse.ArgumentParser(description="Tests ecl's EKF",
+                                     usage=(__file__ +
+                                            " [OPTIONS] [EXPRESSION]"))
+    parser.add_argument('-q', '--quick',
+                        action='store_true',
+                        help='Run only the quick tests')
+    parser.add_argument('-v', '--verbose',
+                        action='store_true',
+                        help='Print verbose output')
+    parser.add_argument('-s', '--stdout',
+                        action='store_true',
+                        help='Print output to stdout during tests')
+    parser.add_argument('-b', '--benchmark',
+                        action='store_true',
+                        help='Run the benchmark tests')
+    parser.add_argument('-p', '--plots',
+                        action='store_true',
+                        help='Create plots during the tests '
+                        '(requires matplotlib and seaborn)')
+    parser.add_argument('tests', type=str, nargs='?',
+                        help='Run only tests which match '
+                        'the given substring expression')
+    args = parser.parse_args()
+    pytest_arguments = [os.path.dirname(os.path.realpath(__file__))]
+    pytest_plugins = []
+
+    if args.quick:
+        pytest_arguments.append('--hypothesis-profile=plots')
+    if args.verbose:
+        pytest_arguments.append('-v')
+        pytest_arguments.append('-l')
+        pytest_arguments.append('--hypothesis-show-statistics')
+    if args.stdout:
+        pytest_arguments.append('-s')
+    if args.benchmark:
+        pytest_arguments.append('-m benchmark')
+        pytest_arguments.append('--benchmark-verbose')
+    else:
+        pytest_arguments.append('--benchmark-disable')
+
+    if args.tests:
+        pytest_arguments.append('-k ' + args.tests)
+
+    # To control plotting, monkeypatch a flag onto pytest (cannot just use a
+    # global variable due to pytest's discovery)
+    pytest.ENABLE_PLOTTING = args.plots
+    if args.plots:
+        pytest_arguments.append('--hypothesis-profile=plots')
+
+    # Run pytest
+    result = pytest.main(pytest_arguments, plugins=pytest_plugins)
+    exit(result)
+
+
+if __name__ == '__main__':
+    main()