Multiple gliders

[woensug-choi]

Multiple glider support is available now.

Each vehicle is affected by separate ocean currents interpolated according to its depth.
This PR includes modifications at the kinematics plugin and an example launch file.

Quickstart

roslaunch glider_hybrid_whoi_gazebo start_demo_kinematics_stratified_current_two_gliders.launch

Changelog

• Kinematics plugin
  • 'Set/get_model_state' ROS-Gazebo generic service calls were not compatible with multiple calls from multiple vehicles. They are alternated to use the SetWorldPos, SetWorldTwist instead
• New launch file
  • 'start_demo_kinematics_stratified_current_two_gliders.launch' file is added
  • Glider names are 'glider_1', 'glider_2'

Notes

• Multiple vehicles example with Glider(AUV)-ASV will be prepared after this. This requires another parameter to let the kinematics plugin know that the model is a surface vehicle
• There are sudden jumps of vehicle positions. It is caused by the bug at the transient current plugin. '/hydrodynamics/current_velocity/glider_1' shows sudden jumps of current velocity. (Sudden jumps at transient ocean current interpolation dave#105) (Fixed with Fix sudden jump of depthIndex dave#106)
• This multiple vehicles support is compatible with tidal oscillation (Tidal oscillation #30)
• Rebased to f375187