Various changes but mostly overhaul of the parsing system using pypeg2.
Implemented the ASP-CORE standard language in ans.py and wrote test
cases, but haven't debugged it yet.

-Peter Mawhorter
Authored some test cases and then figured out that pypeg2 won't work
with my grammar T_T. Started writing my own packrat parser.

-Peter Mawhorter
Much of the implementation of packrat parsing is done (as yet it's
unfinished and untested though).

-Peter Mawhorter
The basic parsing functionality works now for my new custom packrat
parser. Test case coverage isn't great, but a real exercise will be had
by rewriting the parsing functionality in ans.py in the new framework.

Also updated the symbol decorator to work better and allow for
conversion of symbols to custom bools (i.e. False if so desired).

-Peter Mawhorter