Add block for setting line style/pattern

This submission covers addition of the set line style/pattern block. The solid line within the block will return the canvas to using default line drawing behavior. Currently, setting a color after setting a pattern will also return the user to default line drawing behavior.

![screenshot](https://cloud.githubusercontent.com/assets/6125532/4654384/a4350206-54b6-11e4-9bf4-16e70814097e.png)

I actually started with more specific names buut moved to generic names to allow the skins to be populated with different images without confusing name and image. Happy to swap back if that doesn't make sense to you.