Droppable Items expansion

This is a revamp of all the items that enemies can drop.  After a discussion with @CalebJohn I played through the game and found that by killing every single enemy, the amount of gold you could acquire and the amount of health each heard did was almost nothing.  To remedy this i've increased the value of hearts from 5 to 10 and added three new tokens: 10, 100 and 1000.  In addition most of the more difficult enemies now have a chance of dropping a rare material in addition to tokens.  With more materials available potion making will become much easier and the player is encouraged to engage enemies and not just avoid them.

These probabilities and material drops will probably need a lot of playtesting to get the balance right ( @edisonout @didory123 ?)