tigefa4u projects Trac

Refactored the InterTrac unit tests to make it more obvious when we rely on the remote Trac's quickjump facility

InterTrac improvements:
* shorthand InterTrac links for report
* reworked all shortand link syntax to accept the full intertrac name,
not only a 3-letter shortcut, plus optional space.
This makes text like `[trac 2081]` be recognized as a valid InterTrac link.
* and ... '''unit tests''', at last! (only for InterTrac, not yet for InterWiki)

s/ISearchPrivider/ISearchProvider/

TracCrossReferences: support for !ChangesetObject and !SourceObject added

The support for !ChangesetObject has to be improved, though.
In particular, a `resync` won't update the cross-references
for the changesets.

TracCrossReferences: a !TracObject can be either "cheap" or "complete"

It's essential that !TracObjects could be created with minimal cost,
for easily accessing all the basic functionality expected from a Trac object
(`shortname()`, `href()`, `wiki_to_*()` and all the xref facilities).

But at the sub-class level, the Trac object generally needs
to be filled with some data from the db in order to be useful.

The first goal (''"cheap" Trac object'') is achieved by using
either the `TracObject.factory()` or the sub-class constructor
''without'' specifying the `id` of the object.
The `id` is specified after the fact by using `TracObject.setid()`.
By the way, the factory itself rely on that mechanism.

The second goal (''"complete" Trac object'') is achieved by
giving the `id` parameter to the sub-class constructor,
or by calling `TracObject.reload()` on a "cheap" !TracObject.

Adopt SVN-like peg revision notation, as suggested in #2011.

`source:` links can now use the "@" delimiter instead of the "#" delimiter
for targeting a specific revision.

Note that the old way is still supported for backward compatibility.

Refactored the rendering of attachements and repository files so that they share the same code. Fixes #1345.

Sort the project listing in a case-insensitive way. Fixes #2088.

Cosmetic fixes (PEP:8) for `svn_fs.py`

Fixed ''search'' and ''query'' URIs so that the ampersands they eventually contain are escaped only once. Fixes #2042.