Add lexing, parsing for KINETIC, reactions

* Make verbose printing in test_modcc a runtime flag `-v`.
* Show results of `lexer.parse()` in test_modcc when run with `-v`.
* Split numerical lexing and parsing into real and integer categories.
* Add expression parsing for KINETIC block and enclosed reaction
  expressions.

Note: does not parse CONSERVE yet; no test for KINETIC block
(reactions are covered though.)