Add progress and status indicator when moving out of edit mode

[techninja]

For long/complex graphics, many elements may need to be converted/adjusted (as in #139), therefore we need to intercept the Edit mode unload, show a modal window for conversion status and full progress percentage.

See https://github.com/evil-mad/robopaint/blob/master/resources/scripts/robopaint.method-draw.js#L86

[RI0]

My sister suggested this : what if the progress image was an animation of a paintbrush swirling around in paint or possibly mixing two colours together.

[techninja]

Um......sure, why not. Unfortunately we don't have any designers/artists on staff, know anyone that could draw the animation?

[techninja]

Good news everyone! in the next version, Paper.JS handles pretty much any SVG path conversion for us, so we don't have to do it on exit! All the slow code that needed this has been removed.