Added descrimination between left/right arm feature constraints controller.
Added a doc-string.
Added auxiliary functions to start/stop the velocity-resolved controllers.
Added auxiliary generic function to execute a set of constraints
Adapted ketchup-example to use new interface of the send-command/config functions.
Removed two unnecessary comments.
Removed example of grasping a ketchup bottle using the feature constraints controller. Went into its own file.
Added test-example of how to use the feature constraints controller on the PR2 in its own file.