JavaDoc also for traits generated interfaces 

Change-Id: If495086233882d4f9a91a04a6595b42f76ac79fd
added google inject and guava sources to tp

Change-Id: I2f3438d444052dd4968b65b36067eb12c91001ce
updated to Xtext 2.6.1

Change-Id: Idd59ae2f1f981558d315e3eb738a522232453024