Feature/gazebo dex wrist

[hello-fazil]

This PR does the following modification to the Stretch Gazebo package:

• Adds Pitch and Roll control working for the keyboard_teleop_node
  • The keyboard teleop node reads a bool ros param named /stretch_gazebo/dex_wrist loaded through the gazebo launch before initializing the trajectory client for dexwrist.
• By default all the DexWrist configuration files required for stretch_gazebo package is now available within the package (Previously needs to be copied from stretch_tool_share)
• The robot in gazebo can be easily launched in DexWrist configuration or Standard Gripper configuration using the argument "dex_wrist".
  • e.g. : roslaunch stretch_gazebo gazebo.launch dex_wrist:=true
  • The gazebo.launch would automatically choose the appropriate URDF and load right controllers.
  • The urdf folder now has two files
  • stretch_gazebo_dex_wrist.urdf.xacro
  • stretch_gazebo_standard_gripper.urdf.xacro