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)

Tools/simulation/jsbsim/sitl_run.sh

@@ -0,0 +1,96 @@
+#!/usr/bin/env bash
+
+
+set -e
+
+if [ "$#" -lt 5 ]; then
+	echo usage: sitl_run.sh sitl_bin model world src_path build_path
+	exit 1
+fi
+
+if [[ -n "$DONT_RUN" ]]; then
+	echo "Not running simulation (DONT_RUN is set)."
+	exit 0
+fi
+
+sitl_bin="$1"
+model="$2"
+world="$3"
+src_path="$4"
+build_path="$5"
+
+echo SITL ARGS
+
+echo sitl_bin: $sitl_bin
+echo model: $model
+echo world: $world
+echo src_path: $src_path
+echo build_path: $build_path
+
+rootfs="$build_path/rootfs" # this is the working directory
+mkdir -p "$rootfs"
+
+# To disable user input
+if [[ -n "$NO_PXH" ]]; then
+	no_pxh=-d
+else
+	no_pxh=""
+fi
+
+export PX4_SIM_MODEL=${model}
+export PX4_SIM_WORLD=${world}
+
+# This is needed for aircraft namespace mapping
+# Need more architectural discussions to make this more scalable
+case "$model" in
+        rascal)
+            MODEL_NAME="Rascal110-JSBSim"
+            ;;
+        malolo)
+            MODEL_NAME="Malolo1"
+            ;;
+        quadrotor_x)
+            MODEL_NAME="quadrotor_x"
+            ;;
+        hexarotor_x)
+            MODEL_NAME="hexarotor_x"
+            ;;
+        *)
+            echo "Unknown Model"
+            exit 1
+
+esac
+
+export JSBSIM_AIRCRAFT_MODEL="$MODEL_NAME"
+
+if [[ -n "$HEADLESS" ]]; then
+	echo "not running flightgear gui"
+else
+	export FG_AIRCRAFT="${SRC_DIR}/Tools/simulation/jsbsim/jsbsim_bridge/models"
+
+	fgfs --fdm=null \
+		--native-fdm=socket,in,60,,5550,udp \
+		--aircraft=$JSBSIM_AIRCRAFT_MODEL \
+		--airport=${world} \
+		--disable-hud \
+		--disable-ai-models &> /dev/null &
+	FGFS_PID=$!
+fi
+
+"${build_path}/build_jsbsim_bridge/jsbsim_bridge" ${model} -s "${src_path}/Tools/simulation/jsbsim/jsbsim_bridge/scene/${world}.xml" 2> /dev/null &
+JSBSIM_PID=$!
+
+pushd "$rootfs" >/dev/null
+
+# Do not exit on failure now from here on because we want the complete cleanup
+set +e
+
+sitl_command="\"$sitl_bin\" $no_pxh \"$build_path\"/etc"
+
+echo SITL COMMAND: $sitl_command
+eval $sitl_command
+
+popd >/dev/null
+
+kill $JSBSIM_PID
+kill $FGFS_PID