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/jmavsim/jmavsim_run.sh

@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+
+set -e
+
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+cd "$SCRIPT_DIR/jMAVSim"
+
+port=4560
+extra_args=
+baudrate=921600
+device=
+ip="127.0.0.1"
+protocol="tcp"
+while getopts ":b:d:u:p:qsr:f:i:loat" opt; do
+	case $opt in
+		b)
+			baudrate=$OPTARG
+			;;
+		d)
+			device="$OPTARG"
+			;;
+		u)
+			protocol="udp"
+			;;
+		i)
+			ip="$OPTARG"
+			;;
+		p)
+			port=$OPTARG
+			;;
+		q)
+			extra_args="$extra_args -qgc"
+			;;
+		s)
+			extra_args="$extra_args -sdk"
+			;;
+		r)
+			extra_args="$extra_args -r $OPTARG"
+			;;
+		l)
+			extra_args="$extra_args -lockstep"
+			;;
+		o)
+			extra_args="$extra_args -disponly"
+			;;
+		a)
+			extra_args="$extra_args -fw" # aircraft model
+			;;
+		t)
+			extra_args="$extra_args -ts" # tailsitter model
+			;;
+		\?)
+			echo "Invalid option: -$OPTARG" >&2
+			exit 1
+			;;
+	esac
+done
+
+if [ "$device" == "" ]; then
+	if [ "$protocol" == "tcp" ]; then
+		device="-tcp $ip:$port"
+	else
+		device="-udp $port"
+	fi
+else
+	device="-serial $device $baudrate"
+fi
+
+if [ "$HEADLESS" = "1" ]; then
+    extra_args="$extra_args -no-gui"
+fi
+
+ant create_run_jar copy_res
+cd out/production
+
+java -XX:GCTimeRatio=20 -Djava.ext.dirs= -jar jmavsim_run.jar $device $extra_args

Tools/simulation/jmavsim/sitl_run.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+
+set -e
+
+if [ "$#" -lt 3 ]; then
+	echo usage: sitl_run.sh sitl_bin debugger src_path build_path
+	exit 1
+fi
+
+sitl_bin="$1"
+debugger="$2"
+src_path="$3"
+build_path="$4"
+
+echo SITL ARGS
+
+echo sitl_bin: $sitl_bin
+echo debugger: $debugger
+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
+
+jmavsim_pid=`ps aux | grep java | grep "\-jar jmavsim_run.jar" | awk '{ print $2 }'`
+if [ -n "$jmavsim_pid" ]; then
+	kill $jmavsim_pid
+fi
+
+export PX4_SIM_MODEL="iris"
+
+# Start Java simulator
+"$src_path"/Tools/simulation/jmavsim/jmavsim_run.sh -r 250 -l &
+SIM_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: $sitl_command
+
+if [ "$debugger" == "lldb" ]; then
+	eval lldb -- $sitl_command
+elif [ "$debugger" == "gdb" ]; then
+	eval gdb --args $sitl_command
+elif [ "$debugger" == "valgrind" ]; then
+	eval valgrind --track-origins=yes --leak-check=full -v $sitl_command
+elif [ "$debugger" == "callgrind" ]; then
+	eval valgrind --tool=callgrind -v $sitl_command
+else
+	eval $sitl_command
+fi
+
+popd >/dev/null
+
+pkill -9 -P $SIM_PID
+kill -9 $SIM_PID