* Changed preferences to cache them for reading (Yeay!)

* Changed preferences to cache them for reading (Yeay!)
* Prefereneces now remove empty preferences, invalid lines, etc.
* Message highlighting numbering is now semi-automatic (the numbers are
  'corrected' when the preference file is loaded)
* Changed the chosen_theme stuff in load_prefs.php to not erase the filename
  of the theme it is trying to load
* Removed more warnings

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@1178 7612ce4b-ef26-0410-bec9-ea0150e637f0