simulation organization and cleanup

- new modules/simulation directory to collect all simulators and related modules
 - new Tools/simulation directory to collect and organize scattered simulation submodules, scripts, etc
 - simulation module renamed to simulator_mavlink
 - sih renamed to simulator_sih (not a great name, but I wanted to be clear it was a simulator)
 - ignition_simulator renamed to simulator_ignition_bridge
 - large sitl_target.cmake split by simulation option and in some cases pushed to appropriate modules
 - sitl targets broken down to what's actually available (eg jmavsim only has 1 model and 1 world)
 - new Gazebo consistently referred to as Ignition for now (probably the least confusing thing until we fully drop Gazebo classic support someday)

ROMFS/px4fmu_common/init.d-posix/airframes/10040_quadx

@@ -9,6 +9,8 @@
 
 . ${R}etc/init.d/rc.mc_defaults
 
+PX4_SIMULATOR=${PX4_SIMULATOR:=sihsim}
+PX4_SIM_MODEL=${PX4_SIM_MODEL:=quadx}
 
 # disable some checks to allow to fly:
 # - with usb

ROMFS/px4fmu_common/init.d-posix/airframes/10041_airplane

@@ -8,6 +8,8 @@
 
 . ${R}etc/init.d/rc.fw_defaults
 
+PX4_SIMULATOR=${PX4_SIMULATOR:=sihsim}
+PX4_SIM_MODEL=${PX4_SIM_MODEL:=airplane}
 
 # disable some checks to allow to fly:
 # - with usb

ROMFS/px4fmu_common/init.d-posix/airframes/10042_xvert

@@ -8,6 +8,9 @@
 
 . ${R}etc/init.d/rc.vtol_defaults
 
+PX4_SIMULATOR=${PX4_SIMULATOR:=sihsim}
+PX4_SIM_MODEL=${PX4_SIM_MODEL:=xvert}
+
 param set-default VT_ELEV_MC_LOCK 0
 param set-default VT_TYPE 0
 param set-default VT_FW_DIFTHR_EN 1

ROMFS/px4fmu_common/init.d-posix/airframes/4001_x3

@@ -7,6 +7,10 @@
 
 . ${R}etc/init.d/rc.mc_defaults
 
+PX4_SIMULATOR=${PX4_SIMULATOR:=ignition}
+PX4_SIM_MODEL=${PX4_SIM_MODEL:=x3}
+PX4_SIM_WORLD=${PX4_SIM_WORLD:=default}
+
 param set-default SYS_CTRL_ALLOC 1
 
 param set-default CA_AIRFRAME 0
@@ -28,19 +32,19 @@ param set-default CA_ROTOR3_PX -0.13
 param set-default CA_ROTOR3_PY 0.20
 param set-default CA_ROTOR3_KM -0.05
 
-param set-default SIM_GZ_FUNC1 101
-param set-default SIM_GZ_FUNC2 102
-param set-default SIM_GZ_FUNC3 103
-param set-default SIM_GZ_FUNC4 104
+param set-default SIM_IGN_FUNC1 101
+param set-default SIM_IGN_FUNC2 102
+param set-default SIM_IGN_FUNC3 103
+param set-default SIM_IGN_FUNC4 104
 
-param set-default SIM_GZ_MIN1 150
-param set-default SIM_GZ_MIN2 150
-param set-default SIM_GZ_MIN3 150
-param set-default SIM_GZ_MIN4 150
+param set-default SIM_IGN_MIN1 150
+param set-default SIM_IGN_MIN2 150
+param set-default SIM_IGN_MIN3 150
+param set-default SIM_IGN_MIN4 150
 
-param set-default SIM_GZ_MAX1 1000
-param set-default SIM_GZ_MAX2 1000
-param set-default SIM_GZ_MAX3 1000
-param set-default SIM_GZ_MAX4 1000
+param set-default SIM_IGN_MAX1 1000
+param set-default SIM_IGN_MAX2 1000
+param set-default SIM_IGN_MAX3 1000
+param set-default SIM_IGN_MAX4 1000
 
 param set-default MPC_THR_HOVER 0.60

ROMFS/px4fmu_common/init.d-posix/airframes/6001_x4

@@ -7,6 +7,10 @@
 
 . ${R}etc/init.d/rc.mc_defaults
 
+PX4_SIMULATOR=${PX4_SIMULATOR:=ignition}
+PX4_SIM_MODEL=${PX4_SIM_MODEL:=x4}
+PX4_SIM_WORLD=${PX4_SIM_WORLD:=default}
+
 param set-default SYS_CTRL_ALLOC 1
 
 param set-default CA_AIRFRAME 0
@@ -36,26 +40,26 @@ param set-default CA_ROTOR5_PX  0.25
 param set-default CA_ROTOR5_PY  0.15
 param set-default CA_ROTOR5_KM -0.05
 
-param set-default SIM_GZ_FUNC1 101
-param set-default SIM_GZ_FUNC2 102
-param set-default SIM_GZ_FUNC3 103
-param set-default SIM_GZ_FUNC4 104
-param set-default SIM_GZ_FUNC5 105
-param set-default SIM_GZ_FUNC6 106
+param set-default SIM_IGN_FUNC1 101
+param set-default SIM_IGN_FUNC2 102
+param set-default SIM_IGN_FUNC3 103
+param set-default SIM_IGN_FUNC4 104
+param set-default SIM_IGN_FUNC5 105
+param set-default SIM_IGN_FUNC6 106
 
-param set-default SIM_GZ_MIN1 150
-param set-default SIM_GZ_MIN2 150
-param set-default SIM_GZ_MIN3 150
-param set-default SIM_GZ_MIN4 150
-param set-default SIM_GZ_MIN5 150
-param set-default SIM_GZ_MIN6 150
+param set-default SIM_IGN_MIN1 150
+param set-default SIM_IGN_MIN2 150
+param set-default SIM_IGN_MIN3 150
+param set-default SIM_IGN_MIN4 150
+param set-default SIM_IGN_MIN5 150
+param set-default SIM_IGN_MIN6 150
 
-param set-default SIM_GZ_MAX1 1000
-param set-default SIM_GZ_MAX2 1000
-param set-default SIM_GZ_MAX3 1000
-param set-default SIM_GZ_MAX4 1000
-param set-default SIM_GZ_MAX5 1000
-param set-default SIM_GZ_MAX6 1000
+param set-default SIM_IGN_MAX1 1000
+param set-default SIM_IGN_MAX2 1000
+param set-default SIM_IGN_MAX3 1000
+param set-default SIM_IGN_MAX4 1000
+param set-default SIM_IGN_MAX5 1000
+param set-default SIM_IGN_MAX6 1000
 
 
 param set-default MC_PITCHRATE_D 0.0016