This is a simple change to help out the Mac Crowd.  It just changes the name of Startup to OpenRocket so the the menu bar says OpenRocket instead of Startup.

This gets around the very fragile OS X setup thing we have trying and failing at with the mac java client
Changed startup class to OpenRocket
Merge pull request #217 from enderw88/Change-Startup-OpenRocket

Really fix Mac menu name issue.