Add Player Character to Game

[jakeHaasBlog]

Player should move along a grid like in the original pokemon games. Tiles will also be rendered on this grid. Don't need to worry about animations or making it look good yet.

• [x] Player sprite can move up, down, left, and right
• [x] Player has a sprite and is rendered
• [x] Public function to query player's integer position

[jakeHaasBlog]

Also prevented player from walking on un-walkable tiles