Improve processing with ROIs

[aaime]

jai-ext is generally pretty slow at doing image processing with ROIs, part of it is due to the extra accesses and computation, however, it's not all:

• Unlike JAI, operations specific for binary images are missing (e.g., scale, warp)
• Extracting values from the ROIs with iterators is not particularly efficient, dedicated iterators for binary images should be developed
• Thinking out loud, there is no support for marking/recognizing that a ROI tile is completely full or completely empty, which would help speed wise (the only ROI tiles that are interesting are the border ones)