Sprite image enabling/disabling now works

Made changes to the SpriteItem paint() function. Now sprite image
enabling/disabling works. It's also cleaner and easier to read.
Remove NSMBLib

Goodbye, NSMBLib. TPLLib effectively replaces it. Eventually TPLLib will
have a fast Cython version, and maybe even a pure-C version.
Make entrances types 0 & 1 resize for multiplayer

Now entrance types 0 and 1 will show the space needed for all 4 players
in multiplayer levels. Also, some random cleanup.
Add vine entrance preview

Neat little feature that shows you a preview of a Vine entrance.