Move ORM_Validation_Exception overload from gallery_unittest --> gallery.

--HG--
rename : modules/gallery_unittest/classes/GalleryUnittest/ORM/Validation/Exception.php => modules/gallery/classes/Gallery/ORM/Validation/Exception.php
rename : modules/gallery_unittest/classes/ORM/Validation/Exception.php => modules/gallery/classes/ORM/Validation/Exception.php
Make ORM_Validation_Exceptions messages more instructive.
Most of this was already implemented for unit tests... just extended it a bit.