0.12dev: Final fixes for #7715.
0.12dev: Final fixes for #7715.

 * Reverted part of [8279] and added a note when a merge property change has no actual effect.
 * Changed wording to be consistent with Subversion ("reverse-merged" instead of "un-merged").
 * Fixed display of removed merge sources.


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@8280 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac