add associated simulation files

src/CMakeLists.txt

src/actor_collision/ActorCollisionsPlugin.cc

src/actor_collision/ActorCollisionsPlugin.hh

src/actor_collision/CMakeLists.txt

src/actor_collision/actor_collisions.world

src/actor_collision/actor_collisions.world.erb

src/actor_collision/package.xml

src/gem_simulator/gem_description/CMakeLists.txt

src/gem_simulator/gem_description/LICENSE

src/gem_simulator/gem_description/config_rviz/gem.rviz

src/gem_simulator/gem_description/config_rviz/gem_mp3.rviz

...m_simulator/gem_description/config_rviz/gem_velodyne.rviz

...ator/gem_description/config_rviz/gem_velodyne_stereo.rviz

src/gem_simulator/gem_description/launch/gem_vehicle.launch

src/gem_simulator/gem_description/meshes/base_link.STL

src/gem_simulator/gem_description/meshes/chair_link.STL

src/gem_simulator/gem_description/meshes/door_link.STL

...em_simulator/gem_description/meshes/front_camera_link.STL

...m_description/meshes/front_left_emergency_button_link.STL

...tor/gem_description/meshes/front_left_head_light_link.STL