Ignition name changes: ign_* => ign-*
Playing around with ogre 1.8 and 1.9.

 - For now they live in separate formula, but only for testing.
 - Eventually if ogre and rviz work with 1.9, we should update the
   ogre formula to 1.9 (and maybe keep versioned formulae areound)
 - The 1.8 formula builds on Mavericks, but since 1.8 did not really
   support libc++ and I more or less blindly backported some patches
   from 1.9 to make it compile, I am pretty sure that there are runtime
   issues. Focus should be on 1.9
Add devel branch for ogre1.9.