replaced GLKTextureLoader completely, now loading all textures manually.

That class caused numerous problems in the past, especially concerning premultiplied alpha. Apple somehow managed to change its behaviour in every single iOS release ... :|
added factory method to SPRectangle
deactivated mipmaps for TrueType textfields (for faster textfield creation)
added new classes to main Sparrow header file
fixed that new SPAVSoundChannel did not obey master volume
Merge pull request #13 from Gamua/master

merge