Fixed FAIclass selection

Fixed FAIclass selection
	-	Added check for no longer available Server Urls
	-	Added check for classes which can't be found in current
		server/release combination and which also can't be found
		on any other combination ...
	- 	Fixed class selectction
		. Only classes of the current release will be displayed
			(If siga was selected, also siga/rc0.9.2 was displayed)
	-	Sometimes the selectboxes lost all there functionality.

git-svn-id: https://oss.gonicus.de/repositories/gosa/trunk@2826 594d385d-05f5-0310-b6e9-bd551577e9d8