tigefa4u projects Trac

vc-refactoring: change the way a backend is specified

Now, the trac.ini has to be setup like this:
{{{
[trac]
repository_type = hg
repository_dir = /usr/local/hg/repos
}}}

By default the `repository_type` is "svn", so nothing will change
for SVN users.

Also, did a few renamings:
* s/IScmBackend/IRepositoryConnector/
* s/ScmBackendManager/RepositoryManager/

vc-refactoring: in trac-admin, handle the situation when no repository_dir is specified during ''initenv''

HTML escape the author (Mercurial user names are often including the e-mail address, and that was missing from the revision log because it was interpreted as an invalid element...)

TracMercurial: found a way to propagate options to the !HgRepository (inspired from Jason Parks, from his perforce-trac work)

Make it possible to specify the repository during ''initenv'', even if the actual support libraries or plugin are missing

TracDiff: Also show the ''View changes...'' button on the TracBrowser's ''root'' page

TracDiff: Use ''GET'' instead of ''POST'' for the generalized diff query

TracDiff: Use the same layout for the Revision Log diff column as the one in the Wiki diff

Make svn ignore local .hg repository, if present.

TracMercurial: updated the README with the new location of the source