Implement Text Rendering

[colemancda]

• The goal of this feature is to implement NSString.drawWithRect(). Fonts have been added to Silica, and the main rendering code should be done there, NSString.drawWithRect() is for UIKit compatibility.
• Work on this feature is being done on the Text branch in Cacao and the master branch in Silica.
• A PaintCode StyleKit test canvas and unit test case has been added to test this functionality. This feature will be considered done when that unit test renders the same output as PaintCode / UIKit.

[colemancda]

Single line text rendering is working properly, now I need to implement multiline rendering. Not sure whether to create a separate ticket and close this one, or wait till its implemented. I would like to at least have single line Label implemented for #3.