[Insight-developers] Major changes in execution model

[Will Schroeder]

Hi Folks-

We're are heavily reworking the execution model. The purpose is
to make it as easy as possible to understand and learn, and to be
more consistent with the Image->Buffer->Region terminology that
the image iterators currently use.

Lots of renaming has occurred. Extent and Piece terminology have
been unified and are now called a Region. (Previously, an Extent
was used to refer to structured data like images, and Pieces was
a more general term to refer to unstructured data.) We will soon
be adding some additional classes (itkRegion and structured and
unstructured subclasses) to implement and enforce these concepts.

I've checked an initial attempt in, it all builds for me. Please send the
list email if you discover any problems.

Will