Weapon on-strike effects

[kanpov]

Weapons (introduced in #7) are pretty cool, but really boring. And the solution to that is to add a config with a list of effects which will be applied when you hit something firstly on the enemy, secondly on yourself.

[kanpov]

The initial work is done. All that's left to do is to design some weapon configs, so all weapon types can be fully ported to the new engine.