[FINAL] [BOOM!] - Retina Text

:boom: 

Retina text works.

Cherry-picked Isaac's commits from https://github.com/IkeBart/moai-dev/tree/ike-font-op-size-exp .  I *think* I got them all right.

The new code fixes issues with string bounds calculation when a glyphScale is applied to them.  It also fixes an issue where the font size returned for single-line text was sometimes too large.

:boom: