More work on bombs.

Knockback damage can no longer hit a character more than once.

Bombs try hard to always knock back everyone, even whoever's at the epicenter.
Knockback damage now has an optional alternate source logic to help implement
this.

Add tooltip use messages for objects that don't use talents.

Increase rarity of meditation scrolls.  The limits on how often you can focus
and absorb techniques are intended to be a key mechanic.