Tile Editor Menu is functional

-Added in some new classes: Button and TileEditorMenu

-Button class acts like a button, reacts when you click or hover over an
instance.

-TileEditorMenu class inherets from the SideMenu class. It's a more
specific menu for holding buttons specific to editing tiles in the game.

-When you enter edit mode (by pressing "I") the menu that slides out now
holds buttons that represent each tile in the game.

-You can select the tile you want to use (like a brush) to edit the
in-game tiles.