tigefa4u projects Trac

WikiRename: simplify transaction handling in the Wiki model

The !WikiPage public API is not modified. A helper `transaction` function is used to factor out the `handle_ta` business. Its usage is very simple:
- if the function is given a database connection, it will simply execute the callback as part of another transaction,
- if the function has to retrieve a new database connection, it takes responsibility to either `commit` the changes performed by the callback or to `rollback` them, if any exception was raised.

TODO: similar changes could apply to `trac.ticket.model`

Branching WikiRename for implementing #1106

A few clean-ups:
- remove unused variable in wiki/model.py
- typo in wiki_delete.html template

SpamFilter: Fixing a minor glitch with title attributes. Closes #4941.

Small visual fix for label of Inter* links. When used as `[trac🎫1]` it did not show the prefix of 'trac', whereas `trac🎫1` (no brackets) did. Now they both do.

0.10.5dev: ported r6415 (''vc cache fix for postgresql 8.3'')

Adapt version control's cache to PostgreSQL 8.3. A few explicit casts of the revision to a str were missing.

Closes #6274.

Testing: merge through r6137, except r6120 and r6122. All tests pass.

Improvements to the `[[Image]]` macro:

* Absolute URLs now work fine in all cases. Closes #5704.
* Added support for server-relative linking: `//file`
* Added support for project-relative linking: `/file`

The last two work like the new 0.11 syntax for referencing server and project root.

Added a test case for each of the alternatives.

Testing: merge through r6128, except r6120 and r6122. All tests pass.