tigefa4u projects Trac

unicode: synched with trunk.

Experimenting with `ExtensionPoint` descriptors,
and in particular introduced a `SingleExtensionPoint` which
returns a single implementation for a given interface.

This was done by merging the proposal made by trac-form@... in #2403
and what I already did in the FlexibleWikiPageNames branch, i.e.
warn if more than one implementation was active and suggest what
has to be changed in the TracIni file for only selecting one of them.

This has the advantage of re-using the normal way to enable/disable
components from within the TracIni.

In the changeset information, the EDIT changes now contain the exact previous location
and previous revision of the base.

Though this what not a real problem, as Subversion was nevertheless able to find the
correct old content, this provides more useful information in the changeset view.

A `resync` operation is needed to take benefit from this change for old changesets.

Thanks to Antoine Delvaux for noticing and reporting the issue.

spam-filter: add basic filter for reading regex rules from a wiki page called BadContent

Ported attachment link bug fix [2545] to 0.9-stable

add basic extension point for content filtering

create sandbox for spam filtering techniques

Removing db-refactoring branch.

Use more consistent filenames in trac/db.

Merge the db-refactoring branch with trunk.