Abilities, lasting effects and some new unit types

[ozkriff]

Closes #110 - Abilities
Closes #102 - Knockback from heavy strikes
Closes #174 - Fire
Closes #154 - Poison
Closes #175 - Poison cloud
Closes #186 - Hits should take away an attack point from the target
Closes #69 - Bombs
(Maybe it closes some more issues, I could forget something)

The day has come! 🎉
That's a result of two months of non-regular coding.

• New units: alchemist, hammerman, imp_bomber, imp_summoner, imp_toxic
• New objects: bomb, bomb_fire, bomb_poison, poison_cloud, fire
• Active abilities: Knockback, Club, Jump, Poison, Bomb, BombFire, BombPoison, Summon, Dash,
  Rage, Heal
• Auxiliary abilities: Explode, ExplodeFire, ExplodePoison, Vanish
• Passive abilities: HeavyImpact, PoisonAttack, Regenerate, Burn, Poison
• New effects: Create, Vanish, Stun, Heal, Knockback, Fly off, Throw
• Lasting effects: Poison, Stun
• New components: Abilities, PassiveAbilities, Effects, Schedule

And yep, 4K lines in one commit. I'm sorry! 😢 I don't have enough juice to split this mess into neat commits.

[ozkriff]

Ouch, I forgot to rename the branch from WIP_abilities_and_lasting_effects to i110_abilities_and_lasting_effects or something alike.

Agrh, screw it, not that important. Merging the beast!