default functions for Systems.Item
use block_timer from hex.pm
remove attacks, put damage directly on weapons/monsters
disallow equipping items if their skill requirements aren't met
disallow possessing monsters the spirit isn't powerful enough
Bumping version to 0.0.11.
Adding line to CHANGELOG: * skill requirements for armour/weapons,  power requirements for monster possession
Merge branch 'feature/item-re-export'