Because $sitl_command contains quotes

 * this should fix the CI failures where we intermittently saw SIGABRT. (fixes #11144)

This should fix:
- HITL regression (Init MAVLink forever).
- Starting using default arguments.

    - sitl_gazebo in PX4/Firmware (1f9b8333): https://github.com/PX4/sitl_gazebo/commit/c90e8ad2b27b95dc0b4c45b346509477c5fa593d
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/e945745021a74ae45695a624dfc114a5c7bbd6bc
    - Changes: https://github.com/PX4/sitl_gazebo/compare/c90e8ad2b27b95dc0b4c45b346509477c5fa593d...e945745021a74ae45695a624dfc114a5c7bbd6bc

    e945745 2018-12-26 Julian Oes - worlds: fix rate for tailsitter and plane
46a3d27 2018-12-14 Jörg Schmidt - Fix bug in groundtruth altitude calculation

Now that this is merged to master in jMAVSim.

This is just because the branch got merged.

This should fix a race because the use of future/promise wasn't done in
a thread-safe way.

An include was missing.

This fixes a HITL bug and uses promise/future instead of sleeping.

This brings build fixes for Gazebo 7.

This fixes all world files at 250 Hz simulation rate.

This brings support for TCP and lockstep.

This adds the env variable PX4_SIM_SPEED_FACTOR to set the speed factor
to run SITL at.

This switches from UDP to TCP to connect to jMAVSim.

This should be enough for now, especially when we want to raise the
speed of the simulation.

This adds the argument -f for a speed factor to speed up the simulation.

   Delete auto generated vars, and others that were missed.

 - fixes #10972

    - sitl_gazebo in PX4/Firmware (99c225dd): https://github.com/PX4/sitl_gazebo/commit/7c97eeae139d86b3747ea877d8067fb3180dc4f1
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/d08eb5b22d3edfb7a740c883b06f895a173b5519
    - Changes: https://github.com/PX4/sitl_gazebo/compare/7c97eeae139d86b3747ea877d8067fb3180dc4f1...d08eb5b22d3edfb7a740c883b06f895a173b5519

    d08eb5b 2018-11-27 Julian Oes - Update opencv includes

    - sitl_gazebo in PX4/Firmware (dcd12b5f): https://github.com/PX4/sitl_gazebo/commit/5a50cb9a52737522b28abf14ce15b57de8ff2695
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/7c97eeae139d86b3747ea877d8067fb3180dc4f1
    - Changes: https://github.com/PX4/sitl_gazebo/compare/5a50cb9a52737522b28abf14ce15b57de8ff2695...7c97eeae139d86b3747ea877d8067fb3180dc4f1

launch script for jmavsim failed to start if there were any spaces in
paths, string handling in paths was improved and tested.

 - keeping nuttx and armhf compile jobs on 2018-09-11 for now

* attitude and rate setpoint message: use 3D array for thrust demand
* FixedWingAttitudeControl: rework airspeed scaling
  * move airspeed and scaling calculation into separate method
  * if vtol in hover and airspeed disabled use minimum airspeed instead of trim airspeed

    - sitl_gazebo in PX4/Firmware (560a9b45): https://github.com/PX4/sitl_gazebo/commit/3d80f63562c24c1537e1f8423ce649c99ebc15ea
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/2adc86b5bf84543091470966caf33c3b4f3ee666
    - Changes: https://github.com/PX4/sitl_gazebo/compare/3d80f63562c24c1537e1f8423ce649c99ebc15ea...2adc86b5bf84543091470966caf33c3b4f3ee666

    2adc86b 2018-11-14 Elia Tarasov - add max value for wind and wind gust means
fb20a36 2018-11-14 Elia Tarasov - add normal gaussian distribution to wind gust force and direction
bd5ce12 2018-11-14 Elia Tarasov - add normal gaussian distribution to wind force and direction
913c094 2018-11-07 Jacob Schloss - reverse order of test
7d08ef5 2018-11-07 Jacob Schloss - fall back to only enabling up to c++14 on old cmake
0fd93b0 2018-11-07 Jacob Schloss - set CMAKE_CXX_STANDARD so cmake does not append a defualt language standard