Fixes type matchup errors

- Fixes the follwing bugs:
  * A single-type Pokemon's resistances are ignored.
  * Offensive strengths and weaknesses are reversed.
  * x2 resistances are shown as x4 resistances, and vice-versa.
  * Offense table mostly maningless.

- Changes made (aside from bugfixes):
  * Offense table now shows the effectiveness of the most effective
      type of a given Pokemon's types, so that STTAB coverage can
      be evaluated easily.