tigefa4u projects Trac

Follow-up to r4333, fix the attachment unit tests.

The remaining `attachment:` TracLinks tests were moved to tests/wikisyntax.py, with the others already there. Plus added a few `raw-attachment:` tests.

Improved the TracLinks for changesets:
- the "r<revnum>" style has been made more strict; now it only accepts digits, no more hex digits.
- the "[<revnum>]" style still accepts hex digits, but the <revnum> has to have at least 8 digits (12 is common practice)
- the Subversion backend has now a restricted list of aliases for the latest changeset: only "head", "latest", "youngest" or the empty string are now accepted.

Fixes #4261.

calls to `select` method of `Component` and `Version` from r4350 should use it as a class method

0.10.3dev: Ported r4349, fix for #4174 (''sort query by time'')

Encode filename parameter in the Content-Disposition header using
rfc2231 encoding. This fixes #4255.

Fix the `exists()` status for Component and Version.

Thanks to Simon for the report and the testing and to Tim Hatch for the fix.

Closes #4247.

Allow TracQuery results to be ordered by ''created'' and ''modified'' dates. Thanks to Ilias for the initial patch. Fixes #4174.

Follow-up to r4347, there should be a better way to test for Undefined...

Make it possible to examine ticket description changes (#2945).

It is now possible to look at the history of the ticket description field and to visualize the actual changes.
It is also possible to view a ticket at a specified version, in read-only mode.

Next to the ''Description (last modified by <author>)'' title, there's now a (diff) link for showing the differences.
Each description change in the regular change history also features such a (diff) link.

From the diff page, one can go to a ''Ticket History'' view similar to the one of the Wiki page history, this one listing the changes for the ticket description field. From the history view, on can jump to a specific version of the ticket.

Enable `add_stylesheet` etc to generate links outside the `chrome` path: if they start with a slash, they're considered relative to the application root URL, otherwise the link gets prefixed with `chrome/`.