Simple uniform way to extract optional arguments from oiio commands
oiiotool --fit improvements: fix subtle bugs with aspect ratio preservation
for images with differing data and display windows; allow "filter=..."
option to select the filter (as originally advertised but not implemented).
IBA::resize() improvement -- instead of "clamping" at the image edge, just
don't consider nonexistant pixels at all. This solves some artifacts for
certain resize situations, as well as simplifying the logic.
Merge pull request #552 from lgritz/lg-fit

Fixes to oiiotool --fit and IBA::resize