request #6839: unable to use project references in svn commit message

Move validation of commit message done in PreRevChange hook in a
dedicated object to be used in the pre-commit hook.

Change-Id: Ia17b0ce44c0ae1c0ea4c23f11817352ed03e2d01
Merge commit 'refs/changes/09/2409/3' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  request #6839: unable to use project references in svn commit message

Change-Id: Ifa8d54e02e2eef558c7191b7b2e2873d31a0a90b
This is Tuleap 7.0.99.11

Change-Id: I23e70cf7a7829fa80299650c74bc2ff8b6392aab