Expand test framework and test cases (#685)

* Fix comment

* Ekf wrapper for testing

Add utility function for accessing information in the ekf object

* Add step function for Gps sensor

* Add RangeFinder and Flow to simulated sensors

* Add first fusion logic tests

* Add units to function name

* Use EXPECT_TRUE

* Adding missing qualifiers

* Improve EXPECT_ calls

* Improve naming

test/sensor_simulator/CMakeLists.txt

@@ -34,11 +34,14 @@
 
 set(SRCS
 	sensor_simulator.cpp
+	ekf_wrapper.cpp
 	sensor.cpp
 	imu.cpp
 	mag.cpp
 	baro.cpp
 	gps.cpp
+	flow.cpp
+	range_finder.cpp
    )
 
 add_library(ecl_sensor_sim ${SRCS})