A more general fix for selects in NLG preprocessing

If there is a number suffix in the slot ID, it gets removed
before performing preprocessing, so that the same actions
are applied to `vehicle1` and `vehicle` etc.
Use specified vehicle type for directions

The policy/CRWS directions search now accept restrictions for
vehicle types (the user can say they only want to go by bus/train etc.
and this will now be reflected in the search).
The possibility to specify the number of transfers

Users now can specify the maximum number of transfers
they will accept.

+ fixes in HDC-SLU for subway, apology()
Merge pull request #60 from UFAL-DSG/nlg_select_fix

A more general fix for selects in NLG preprocessing
Merge pull request #61 from UFAL-DSG/vehicle_spec

The option to use only a specified vehicle type in directions search
Merge pull request #62 from UFAL-DSG/num_transfers

The possibility to specify the number of transfers
Merge branch 'ptics_live' of github.com:UFAL-DSG/alex into ptics_live