Implement Anim Sheet Import

[PsyCommando]

This is going to be a tough one.
Basically, in order to add an animation frame from the outside, we need to import a frame, cut it up into pieces of supported resolution, store it in several images and save the placement data in the newly created frame.

Some of the bigger issues:

• Algorithm to analyze an image, and plan out the needed cuts, or cropping.
• Algorithm to figure out the position a piece of image is when assembling the image.
• Algorithm for splitting up a large sheets into animation frames.
• UI for cropping images.
• UI for importing animation sheets, and pick animation frames.
• Grid snapping algorithm

And the features those allow:

• Export animation sequences to sheet.
• Import frame
• Import animation sequence from image
• Import animation sequence from sprite sheet