Update submodule ecl to latest Sun Dec 22 12:38:19 UTC 2019

    - ecl in PX4/Firmware (f75f3fc): PX4/PX4-ECL@1813034
    - ecl current upstream: PX4/PX4-ECL@490c749
    - Changes: PX4/PX4-ECL@1813034...490c749

    490c749 2019-12-18 kamilritz - Revert if statement swap in resetMagHeading
a6bbafc 2019-12-17 kamilritz - Remove unnecessary initialiseCovariance
ef9f105 2019-12-17 kamilritz - Random improvements
7d3814b 2019-12-17 kamilritz - Add orientation initialization tests
01495ed 2019-12-17 kritz - Clean initialiseFilter function (#687)
532c9ab 2019-12-17 kritz - Expand test framework and test cases (#685)
6c25ac5 2019-12-17 kritz - Tilt Initialisation: Average Filter -> LowPass Filter (#686)
98a1aae 2019-11-26 Daniel Agar - EKF: use Matrix cross product
0831c15 2019-12-16 kamilritz - Move time update to sensor base class
1832bed 2019-12-16 kamilritz - run_seconds
39b369d 2019-12-16 kamilritz - make ekf a shared pointer
f13f2f8 2019-12-16 kamilritz - use shared pointer
00cd720 2019-12-16 kamilritz - Change folder name
b9dd1e5 2019-12-16 kamilritz - Change file names
2d2edd9 2019-12-12 kamilritz - ECL Unit Test Clean Up
6b25dbd 2019-12-12 kamilritz - SensorSimulator
85e0e6e 2019-12-13 kamilritz - Remove resetStates(AndCovariances) function
64652f5 2019-12-09 kamilritz - Improve quality of comments
1bf09fd 2019-12-09 kamilritz - Remove EKF prefix from logged messages
88c4929 2019-12-11 kamilritz - Use helper function to switch to gps height
042d9b6 2019-12-11 kamilritz - Remove dangerous _primary_hgt_source variable
66f707e 2019-12-11 kamilritz - Remove non enterable if statement
cd030e7 2019-12-11 kamilritz - Remove switch to ev hgt during filter initialization
4bc6ae6 2019-12-11 kamilritz - Remove if statement that can not be entered
6941777 2019-12-11 kamilritz - Remove obsolete vision sample counter during initialization