add checkbox to toggle if moveit rviz plugin subscribes
the topics to be used for communication to the external ros nodes.

update moveit_joy.py to parse srdf to know planning_groups and the
names of the end effectors and support multi-endeffector planning groups.
Documentation
Update joystick documentation and rename the
the launch file for joy stick program.
Shorten the message the check box to toggle
communication with joy stick script.
Python wrapper for getEndEffectorTips()
Added wrapper for new function
Remove sample launch file for joystick and update
joystick python script.
1) Use moveit-python binding to parse SRDF.
2) Make the speed slower to control the marker from joystick.
3) Change joystick button mapping to be suitable for the users.
Better user output, kinematic solver error handling, disclaimer
update joystick documentation according to the latest implementation