Support conversion of language levels when importing from older .ext files
* adapt .ext import functionality to react to modified list of language levels
* make sure that Personnel Application Tab includes more validation checks and validation works properly
* improve previous change in clbVersatile so that string list of selected values does not unnecessarily contain quotes unless explicitely stated
merge from trunk
merge from lp:~wbrowa/openpetraorg/dev_0000644_Language_Level