More Hearts item and One Up item added

Added in two more findable items. These don't drop from enemies (To
encourage more exploration). MoreHearts increases the rate of heart
drops from enemies. OneUp is a one-use extra life, using itself up when
the player reaches 0 health, restoring them to 75 health, and giving
them a brief mercy timer to get out of danger. Both of these are opening
to balancing changes.