HDC SLU update

Update of HDC SLU rules and surface forms as discussed on the meeting.

Dictionary method implemented followingly:
* data saved in `PTICS/data/utt2da_dict.txt` in format `utterance tab dialogue_act`
* data loaded in `PTICSHDCSLU` constructor from hard-wired path (relative to `PTICS/slu` directory)
* in the case of match, DA is wrapped in `DialogueActHyp` with confidence 1

Is that ok? Shouldn't the dictionary file path be injected from elsewhere? Are `DialogueActHyp` and `DialogueActConfusionNetwork` interchangable?
Please add comment what is the purpose of utt2da here. And put the loading code into a separate private method like _load_utt2da(fname).