repository-reference for Xtext release site

Change-Id: I437c1939c97af7f7cf0e01260bc32fbb09c190a9
tests for proposal and imports NOT with SwtBot

We can do the same and probably more efficiently with the Plug-in test.

Change-Id: Ife26e34fcf5ab9a80c00cb3db87c412f0a4c276f