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/lint

@@ -0,0 +1,94 @@
+#!/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.
+#
+###############################################################################
+"""Runs code checkers on ecl pytest code
+@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
+
+from subprocess import Popen, PIPE
+import sys
+from datetime import datetime
+
+CHECKERS = [
+    ['pep8', '.'],
+    ['pep8', './ekf_test'],
+    ['pep8', './lint'],
+    ['pylint', './lint', '--reports=n', '--score=n'],
+    ['pylint', './ekf_test', '--reports=n', '--score=n'],
+    ['pylint', './plot_utils.py', '--reports=n', '--score=n'],
+    ['pylint', './test_altitude.py', '--reports=n', '--score=n'],
+    ['pylint', './test_basics.py', '--reports=n', '--score=n'],
+    ['pylint', './test_sampling.py', '--reports=n', '--score=n'],
+    ['pylint', './test_utils.py', '--reports=n', '--score=n'],
+]
+"""List of checkers to run and their arguments
+"""
+
+if __name__ == "__main__":
+    try:
+        TIC = datetime.now()
+        CHECKERS_RUN = 0
+        ERROR = False
+        for checker in CHECKERS:
+            process = Popen(checker, stdout=PIPE)
+            sys.stdout.write('.')
+            sys.stdout.flush()
+            CHECKERS_RUN += 1
+            header = "Output from %s" % " ".join(checker)
+            output = process.communicate()
+            message = ""
+            for elem in output:
+                if elem is not None and elem:
+                    message += elem.decode('utf-8')
+                    ERROR = True
+            if not message == "":
+                print(header)
+                print("=" * len(header))
+                print(message)
+                print("=" * len(header))
+
+        TOC = datetime.now()
+        print("\n" + ''.join(['-']*70))
+        print("Ran %i checkers in %fs\n" % (CHECKERS_RUN,
+                                            (TOC - TIC).total_seconds()))
+
+        if not ERROR:
+            exit(0)
+        else:
+            exit(1)
+    except KeyboardInterrupt:
+        exit(2)