Cmake tex2lyx tests: Take care of initialized userdir

If we are testing tex2lyx the first time, then the userdir
is empty. We call now configure.py to initalize in case it is needed.
The algorithm to detect if reconfigure is needed mimics the lyx behaviour.
Merge remote-tracking branch 'github/build-bot-master' into bleeding-edge-master
2014.09.03-20.00