adds build of gz_msgs on end-user computer
This means we don't need to provide different zips for different
versions of ubuntu.
The problem was that gazebo on 14.04 comes with protobuf 2.5 but gazebo on 15.10 comes with 2.6
added a few other fixes to the install script as well
also fix dependency between simluation publishing and libwpilibcsim
building
Change-Id: I57d5a26ed7795bc61a25402e2986c6023d1d78ac
