[Insight-developers] Reorganized IO directory

[Will Schroeder]

Hi Folks-

I am reorganizing and consolidating the IO related classes into the IO directory. Several IO related filters were in BasicFilters (Writer, VTKImageWriter, VTKImageReader, vtkRawImageReader, etc.) These have now been removed and are being replaced by the appropriate ImageIOBase subclasses. 

The ImageIO classes (e.g., VTKImageIO) will perform both reading and writing, and the filters ImageFileReader and ImageFileWriter interact with them (and have the ability to create them using an object factory mechanism).

Note that I made an API change in ImageIO - the Load() method has been renamed to Read() to be consistent with the rest of the interface and the other objects.

Some of the classes (ImageFileWriter, VTKImageIO) are not fully functional yet, I wanted to get the reorganization done to get the dashboard to settle down and isolate later changes to the new classes.

Note that I changed several tests that used the obsoleted VTK and Raw readers/writers.

Please contact me if there are any problems or questions.

Will