Cleanup

- Removed CEGUI, Lua and ObjectiveLua dependencies [CMakeLists.txt]
- Removed the ObjectiveLua submodule [.gitmodules]
Merge remote-tracking branch 'upstream/restart' into restart

- Merge with latest changes from upstream. I had already started deconflicting a merge with the previous commit on the upstream branch and decided to hold off merging this minor change till now.