Faster JavaScript-only PNG resize with higher quality rescale algorithm.

[daithiocrualaoich]

Find/implement a faster pure JavaScript PNG resize. Needs to be pure JavaScript to operate on the JavaScript side of the CocoaScript bridge. Provide higher quality rescale algorithms like bicubic interpolation, etc.

Alternatively, implement the PNG scaling on the ObjectiveC side of the Cocoascript bridge, e.g. https://stackoverflow.com/questions/14238870/cocoa-objective-c-how-to-resize-a-png-image.