Allows reading of generic content from tmx.
Background image and bricks.
Merge branch 'master' of https://github.com/rliebz/Puddle

Conflicts:
	Content/Level1.tmx
Makes jetpack class into generic powerup class.
Improves method and variable naming.
Buttons and refactor sprite draw method.
Merge branch 'master' of https://github.com/rliebz/Puddle

Conflicts:
	Content/Level1.tmx
Buttons animating.
Y collision box for buttons fixed.