[Feature Request] Multiple crop sizes (v2.2.0)

[lithiumlab]

It would be awesome this Extra supports multiple thumb sizes creation. I guess the data can be stored the same way it is now only the crop part of the json would be multiple (an array). Guess the sourceImg part of it can be the same.

Providing a UI to rapidly set manual crop (art direction) for images.

Something like this:
http://s.w.org/plugins/post-thumbnail-editor/screenshot-4.jpg?r=864370

I'll love to help to contribute to make this feature possible.
Let me know your thoughts.

[lithiumlab]

Behavior for not yet manually modified thumbnails can be to return the image with predefined dimensions and zc=1. So you can still call that thumb size and produce an acceptable thumbnail even if not manually cropped yet.

Another consideration may be a shorthand for calling the thumb predefined sizes something like:

[[*tvname:thumb=`small`]] , [[*tvname:thumb=`medium`]]  or even shorter:  [[*tvname:th=`large`]]

or any name the user likes to use in the image+ configuration for the thumbs.

calling only [[*tvname]] can return the 'default' or first item of the crop settings array.

Just thoughts...