Gen 1: Learnset bug fixes

Poliwhirl learns skullbash, not skullbasg.
Pidgeotto must be listed just once.
Gen 1: Fix poison and burn damage

In gen 1, poison and burn damage is 1/16 of max hp, not 1/8.
Gen 1: Bide lasts from 2 to 3 turns

Bide lasts from 2 to 3 turns after it's used to store at least 
two turns of damage, so it's 3-4 on duration.
Gen 1: Add pidgeot learnset

Added pidgeot learnset.
Merge pull request #186 from Joimer/patch-8

Gen 1: Bug fixes