Improved isCurrentRevision(), tests included
refactor PageRevisionLog into Media- and PageChangelog extending Changelog
fix not updated call, renaming
improve unittests getrelativerevision. Bit code reformatting unit tests
Merge remote-tracking branch 'remotes/splitbrain/diff_navigation' into revisions
fix function name media_isexternal()
remove empty rev from ml()
rename getProperRevision() to getLastRevisionAt()
make getLastRevisionAt() a method of ChangeLog