Support forInterWiki links

(since [milestone:0.10])

Definition

AnInterWiki link can be used for referring to a Wiki page
located in another Wiki system, and by extension, to any object
located in any other Web application, provided a simple URL
mapping can be done.

At the extreme,InterWiki prefixes can even be used to simply introduce
links to new protocols, such as tsvn: used byTortoiseSvn.

Link Syntax

<target_wiki>(:<identifier>)+

The link is composed by the targeted Wiki (or system) name,
followed by a colon (e.g. MeatBall:@),
followed by a page specification in the target.
Note that, as forInterTrac prefixes, _InterWiki prefixes are case insensitive*.

The target Wiki URL is looked up in theInterMapTxt wiki page,
modelled afterMeatBallInterMapTxt.

In addition to traditionalInterWiki links, where the target
is simply appended to the URL,
Trac supports parametricInterWiki URLs:
identifiers $1, $2, ... in the URL
will be replaced by corresponding arguments.
The argument list is formed by splitting the page identifier
using the ":" separator.

Examples

If the following is an excerpt of theInterMapTxt page:

h1.InterMapTxt =
 This is the place for definingInterWiki prefixes ==

Currently active prefixes: [InterWiki]]

This page is modelled after theMeatBallInterMapTxt page.
In addition, an optional comment is allowed after the mapping.
----
<pre>
PEP      http://www.python.org/peps/pep-$1.html           # Python Enhancement Proposal $1 
Trac-ML  http://thread.gmane.org/gmane.comp.version-control.subversion.trac.general/$1  # Message $1 in Trac Mailing List

tsvn     tsvn:                                            # Interact withTortoiseSvn
...
MeatBall http://www.usemod.com/cgi-bin/mb.pl?
MetaWiki http://sunir.org/apps/meta.pl?
MetaWikiPedia http://meta.wikipedia.org/wiki/
MoinMoin http://moinmoin.wikiwikiweb.de/
...
</pre>

Then,

• MoinMoinInterWikiMap@ should be rendered asMoinMoinInterWikiMap
  and the title for that link would be "!InterWikiMap in MoinMoin"
• Trac-ML:4346 should be rendered as Trac-ML:4346
  and the title for that link would be "Message 4346 in Trac Mailing List"

----
See also:InterTrac,InterMapTxt