Refs #1077. Improved speed of the IndexedBySite archive type by optimizing the case when launching the archiving process is disabled. Instead of selecting archive IDs one at a time, IndexedBySite will now select them all at once.

Notes:
* Also added an integration test that will test whether Piwik works when archiving is disabled.
* Modified getKnownSegmentsToArchive() to cache its result as static function data instead of having ArchiveProcessing cache it as instance data.
* Changed several instance methods in ArchiveProcessing to static methods. These methods are responsible for determining if archiving is disabled.
* Removed meaningless idSite related code from TablePartitioning.


git-svn-id: http://dev.piwik.org/svn/trunk@5475 59fd770c-687e-43c8-a1e3-f5a4ff64c105