Removed nasty hack for drawing paths over paths

And therefore removed extra jQuery dependency
Added colour: White
Minor refactoring

Name change: controlsState -> toolState
Refactored tool controller code
Fixed for Firefox

Although I'm not precisely sure how. The following appear true in firefox:

 - layer on its own does not work

 - offset on its own does not work

 - when the offset polyfill is applied, layer works

 - when the offset polyfill is applied, offset works but too far to
   the right
Minor refactor of clearscreen code
Removed some redundant angular-seed files
Can add static-size circles
Can size the ellipses, albeit a bit strangely
Make eraser tool name more agnostic
Refactored path and ellipse tool code