#change Root module path added to include paths.
#change Plugins now write intermediates to the project folder.
#change All generated #includes are now relative.
#change Updated UHTDebugging.manifest to new format.
#remove Rocket-specific UHT execution removed.
#remove Some bHackHeaderGenerator usage removed.
#remove iOS header hack removed.
#codereview robert.manuszewski,ben.marsh
[CL 2068336 by Steve Robb in Main branch]