New assets for artist NSEW

- Join arrow and artist drawing into one image
- Use separate assets for NSEW
- Pre-set width/height for proper toolbox layout

# Before

![image](https://cloud.githubusercontent.com/assets/206973/3848514/d3b958fa-1e70-11e4-9c22-3e917f70b0e1.png)

# After

![image](https://cloud.githubusercontent.com/assets/206973/3848507/bce23b38-1e70-11e4-816b-9168f4b2d9bc.png)