Added a bunch of useful text management functions.
Consequently, some already available functions like `FormatText()` and `SubText()` has been renamed for consistency. Created temporal fallbacks for old names.
raylib version bumped to 2.3.

Useful for bitmaps pixelated fonts where anti-aliasing is not desired!
Change also enables additional font generation mechanisms in a future (cleartype, hinting...).

- Preparing MP3 files support
- Jumped version to raylib 2.0-dev (too many breaking changes...)

LoadSpriteFontTTF() --> LoadSpriteFontEx()

- Removed rbmf font example
- Reviewed physac examples