Hits and Stats: collectible buffs

[dreammelter]

Implement the Power-up and Buff components to complete our Hits and Stats system.

These components are mostly for the passive items you can buy from the shop but could also be used to quickly give enemies different boosts, too. (The regular power ups could technically use these, too.)

Characters with a Power-up bar are able to use Buffs to boost/reduce their stats.

The Power Up Bar should:

• [ ] communicate with the UI and other components so stats may be adjusted and displayed

Buffs should:

• [ ] contain info for the Power Up Bar to use: icons/images, stat to change, amount to change, and a short description
• [ ] buffs that display in the store should also include price info

[dreammelter]

Buffs would fit pretty nicely into a little database, rather than making 20 different scenes.... but we'll explore both approaches for the class.

[dreammelter]

Buffs could technically be attached w/o the power bar (but I'll come back to this.)