Vast improvements in graphics class accuracy for HTML5 backend

Contributes towards the resolution of #214

Test project: https://dl.dropboxusercontent.com/u/10641626/Github/OpenFL-TestApp.zip

- Fixes bitmapfill on drawn paths
- Implements matrix transforms on bitmap fills
- Fixes other inconsistencies in the graphics class
- Cleans up the graphics class code

This does remove one optimisation for drawing rectangles where using a pattern fill was not needed, however supporting this optimisation makes the code very messy.

Cutting holes by drawing over the current path is semi-supported, not fully supported due to limitations in HTML5 drawing.

Changing line style mid-fill is not supported due to limitations in HTML5 drawing.

#### Test renderings:

__Flash (Target reference):__
![impl_flash](https://cloud.githubusercontent.com/assets/5081038/3131534/9ef95648-e805-11e3-954f-bd8b51cf4b65.png)

__HTML5 After improvements:__
![impl_html5](https://cloud.githubusercontent.com/assets/5081038/3131537/a3fcecd6-e805-11e3-84cc-19b9275a4c20.png)

__OpenFL 2.0.0 HTML5:__
![impl_orig](https://cloud.githubusercontent.com/assets/5081038/3131541/aa8f2a5a-e805-11e3-8e25-b6704d22bd00.png)