remove rosgraph_msgs and std_srvs (moved to separate repo)

The message packages `rosgraph_msgs` and `std_srvs` must be moved to a separate repo (https://github.com/ros/ros_comm_msgs) since currently there is a circular dependency which prevents releasing both repos into *Indigo*. `ros_comm` depends on `roslisp` which depends on those two packages inside `ros_comm`.

While this also applies to *Groovy* and *Hydro* I am not planning to split it for them since the repos are already released and therefore the circular dependency does not pose a problem anymore.

@tfoote @wjwwood Please review.