Playable Lesson Cards

--Main Changes--
Lessons cards are now playable from the hand onto the board, Player
class keeps track of the number of lessons in play and their type.

--Other Misc Changes--
Lowered frame rate down to 30 (from 60) to keep it more stable, may move
it back up if it's too choppy.
LessonTypes can now be converted from string representations ("Charms",
"Potions", etc.) into index representations (0, 1, 2, 3, 4) and vice
versa, this helps with loop iteration and type equality comparisons.
Cards now use the hand cursor when the mouse hovers over them.
Added icon file from previous project, will be implemented when we build
the project with SWFStudio for release version.