Avatar::init: remove hero_cooldown resizing

It's overwritten later on with a newly constructed vector:
	stats.hero_cooldown = vector<int>(POWER_COUNT, 0);

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Move cooldown from statblocks to Avatar

We only need it in Avatar, so move it there.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Merge pull request #789 from stefanbeller/powerlimit

Remove power limit and move hero_cooldown to Avatar