Makes wikilinks nicer when possible

Makes wikilinks nicer when possible

This patch mostly impact Title:getLocalUrl() with two changes:

1) Abstraction:

$wgActionPath related code is now in Title::resolveActionPath(). It now
interprets query parameters using an array which is easier to read than
playing with a regexp and the evil $matches[].

2) Tweaking:

Change the 7 years old (r2621) URL forge:
  "{$wgScript}?title={$dbkey}&{$query}"
  => /w/index.php?title=FOO&q=2

To a nicer
  "str_replace( '$1', $dbkey, $wgArticlePath )"
  => /wiki/FOO?q=2

Additional changes:

* Parser tests were modified to reflect the changes.
* PHPUnit TitleTest amended to test getLocalUrl() (add more!!)
* When using wgActionPaths, makes sure the 'view' action is a sane default