tigefa4u projects Trac

Should fix #2481 in [milestone:0.9]

The RSS feed items from TracRevisionLog link to the restricted changeset.

The advantage is that the sequence of changeset navigation will
stay on the path from which the RSS feed was subscribed.

The full changeset is anyway only one click away...

Use `base_url` when computing absolute URL of redirection (from a patch by cmlenz, on #2553)

Follow-up to r2818: now the `rss_title` function should do what I wanted.

Trac RSS 2.0 feeds should now be valid.

The RSS feeds produced by the TracTimeline, the TracQuery, the TracReport
and the TracRevisionLog should now work as expected.

The following changes have been implemented:
* The item's <title> element should never contain HTML markup,
and only numerical or predefined XML entities are allowed.
* The item's <description> element contains ''escaped'' HTML markup
* Also, the TracRevisionLog RSS feed's <author> elements are not
emitted if there's no author (i.e. no e-mail address for the author)

Closes #2580.

The Changeset timeline event has been improved:
* The RSS title doesn't contain markup anymore
* The readability of the included file listing has been improved
(closes #2072).

TracCrossReferences: bug fix for Ticket timeline bug introduced in r2788

The refactoring of TracCrossReferences continues...

The rebuilding of the cross-references is now done in the `xref.module`.

Consequently, a `ITracObjectManager` has now less to do:
It only has to provide the db type it manages (only one),
the factory method to create the subclass of `TracObject`
that it manages and an iterator over all existing objects
of that kind.

At the `TracObject` level, a bit more generic functionality
concerning the DB interface has been added:
* a `_load` method that can be used to ensure a `TracObject`
is in it's loaded form. `reload` should still be used if
one wants to ''force'' reading from the DB.

The facets are now better handled at the level of each `TracObject`
(there will be soon a `WikiFacet` class again, I guess).

''View changes'' should trigger a `GET`, not a `POST`. Thanks to mgood for the tip.

Title for generalized diff is a bit more compact: ''Changes from `_old_path_` at r`xy` to `_new_path_` at r`yz`''