Alter some identifiers. #207

As per http://bugs.veekun.com/projects/pokedex/wiki/Identifiers?version=3.

- The following tables were handled in commit "2090e34 Move English
  texts to language-specific tables": berry_firmness, item_categories,
  move_battle_styles, move_damage_classes, move_effect_categories,
  pokeathlon_stats, pokemon_colors, pokemon_habitats, regions, types,
  versions.

- These tables are skipped, pending further discussion:
  generations, growth_rates, move_targets, stats.

- Deviations from the wiki:
    - egg_groups: 'no-eggs' is not changed to 'noeggs'
    - encounter_terrains: the 'old-rod' alternative is used.
    - types: 'unknown' is not changed to '???'
    - pokemon_move_methods:
        - 'level-up' is not changed to 'level'
        - 'colosseum-purification' and 'xd-purification' are left alone,
          because colosseum and xd have not yet been added as versions.
        - 'xd-shadow' is left alone for consistency with 'xd-purificaiton'.