Enabled training SLU on multiple sets.
Equipped test.py with arguments (input, model dir)

I also did quite some refactoring, imploding loops into loops for easier
reading and maintenance of the script. When doing that, I think I might
have fixed a bug (using the Utterance constructor for an n-best list).
Merge branch 'mk-develop' into lrc

Conflicts:
	alex/applications/PublicTransportInfoCS/slu/train.py

Merged upstream updates.