Allow Spell Item use while Blind and Dazzled

By allowing potions, scrolls, and wands to be used while Blind and
Dazzled, the power of both immediately drops. The major concern is the
length of Blind on unbuffed targets: now unbuffed targets can drink
Eagle Eyes potions while blind.

This is naturally suited to the recent upgrades to spell items. They now
stack and never expire, so players can farm or make potions as needed
and carry them for important moments.

This is also a parallel weakening of Purge: Shals can't stop you from
drinking a potion because they don't have Hold. You can't completely
rebuff yourself with potions, but you can certainly get up one or two
buffs that really matter.

This proposal:
- nerfs no spells directly at all
- offers a new reaction option so players aren't just running around
like a chicken with its head cut off
- opens up the potion system to a much larger variety of tactics