Argument error checking for quote and math
Support booleans and the ``not`` function
Support the boolean operators ``or`` and ``and``

I also refactored the ``_convert_to_bool`` function to actually return a
boolean instead of a boolean lval.

I also removed some extra crap from the eval.h header.
Support top-level booleans ``T`` and ``F``

I also added documentation on the booleans.