Almost perfected the ResourceManager

Now is able to load textures into sprites in other classes with ease.
Basically, created buildablebitmaptextureatlas, gave it 256x256 size and
the texture sizes for derpman.png and derpman2.png were 64x64. NOTE:
atlas size must be bigger than combined area of images in there. Also,
got the textures to load correctly because I added in the try{}catch{}
statement, which is essential. Also, added Java Garbage collector to the
unload().