[libvoikko] grammar checker loading

[Francis Tyers]

Hello all,

After getting CG grammar loading more or less in a functional place, I
started to look at getting analyses out of the dictionaries. 

I am at a bit of a loss how to move forward. Here are some comments:

* The DictionaryLoader and friends classes don't seem to be overly
friendly to grammar checking. Aside from the name (a grammar checker
isn't a dictionary, although it may contain one). Should there be a new
class for loading / setting up the grammar checker ? This would involve
adding some stuff to voikko_options_t and make a new class to be called
from voikkoInit() which goes and finds valid grammar checkers.

* libvoikko now links with hfst-ospell and not hfst-optimised-lookup.
hfst-ospell can do analyses, but it means encapsulating everything in
a .zhfst file, which might not be what we want. Can we link with both
hfst-optimised-lookup and hfst-ospell ? A further complication(?) is
that the hfst-ospell namespace seems to be called hfst_ol (this confused
me at first).

* These decisions might take some thought, so at the moment I might just
start with linking with hfst-optimised-lookup and hardcoding everything
in the new grammar/HfstAnalysis.cpp. We can always modularise it later.

Regards,

Fran