Add initial implementation of draw lines with pattern block. Still need to add code to pre-load images so lines will always be displayed on first RUN
Added image preloading
Created property to allow easy reference of line style blocks from turtle.js
Removed unneeded path references for pattern images.
Add "set line style" block to turtle/artist app
Merge branch 'staging' of https://github.com/beezwaxz/code-dot-org into staging