tigefa4u projects Trac

Use bound parameters in reports with dynamic variables, so that the possible values do not need to be restricted to safe characters. Fixes #2536.

Remove the support for ''sibling environments'' that InterTrac introduced.

Read the following
[http://thread.gmane.org/gmane.comp.version-control.subversion.trac.devel/159 discussion]
on !TracDev, for the details.

VcRefactoring: moves the support for hexadecimal changeset names from TracMercurial to the core.

As a side effect, I had to make the INTERTRAC_SCHEME non-greedy,
because common shortcuts like `[trac2781]` were interpreted as
`tr` prefix followed by an `ac2781` revision...
Anyway, the greediness was not needed anymore, as I removed
the support for digits in the INTERTRAC_SCHEME

In addition, the TracMercurial plugin reintroduces support for
the `cset:`, `chgset:`, `tag:` and `branch:` link resolvers.
* the first 3 are synonyms and can be used to refer to a
changeset using either a revision hash, a revision
number or a tag name
* the last one is special, as it will refer to the
current ''head'' for that named branch

TracMercurial adapted to work with current trunk or vc-refactoring branch.

There are of course rough spots, but the plugin basically works.
(also tested with the latest hg, i.e. c2755eba8631).

VcRefactoring branch re-created

WorkFlow:

* Switched to `SingletonExtensionPoint`, much cleaner.

WorkFlow:

* Merged log:trunk@...:2867

Remove executable flag from JS file.

add `SingletonExtensionPoint` for components that only need to select a single implementation (see #2403)

TracChangeset failed to show a changeset involving files copied from outside of the scope of the repository subset.

Related to #1830.