Update to JGit 3.1.0

Change-Id: I94d4f6146c79541bf8a36e4c3dca1842e46cddd5
Add raw link to commit, commitdiff, and compare pages (issue-319)

Change-Id: Ifc878cb59fe66674e6dfdc6d233fa26be1f4d605
Fix raw page binary content type when running behind reverse proxy

Change-Id: I9f613114b2bb4c1dacae6e67c7673149a0476cf1