Label block

This replaces #362  and makes the text block a very simple label text block. 

It takes in a string, and a font size (in point values). 

It will:
* Rotate text with the sprite
* Move text to the end of the word
* Draws text at alphabetic baseline
* Always stamp LTR. There will need to be a bit of work done for RTL.

Example:
![screen shot 2014-06-29 at 10 22 34 am](https://cloud.githubusercontent.com/assets/1505907/3423921/a02170cc-ffb2-11e3-9d27-0bd111a033d5.png)

Strange, Maybe we need to make sure that the whole area that's filled by the stamped text gets recorded in the damage list. Perhaps simply calling stage.changed() might help... (even though I swear that must already be called *somewhere*) :-)