Replace PNG sprite with SVG sprite

This should be ready to go. I switched out the PNG sprite with SVG sprite, for resolution independence and it also saves a few KB. Sadly, cursors don't support SVG so those still need to be PNG's.

I also ended up fixing #1246 while working in this branch, so that's part of this pull request too.

It'd be great if someone double checked this before merging. Works fine for me in Safari/Chrome/FF/Opera.