Fix some JPEG files not being recognized, now only look at the first two bytes.
TGA now converts alpha to associated on input if requested, and on output writes
the attribute that indicates if the alpha is premultiplied or not.
TGA output now always writes unassociated alpha, even if the input is associated.
This is because common applications like Gimp, Photoshop and Preview will assume
TGA files to have unassociated alpha.
Fix two issues with unassociated alpha conversion:
* PNG, TIFF and TGA input still had oiio:UnassociatedAlpha set to 1 after they
  convert the alpha to associated.
* PNG output did not take oiio:UnassociatedAlpha into account to determine if
  conversion should be done, while TIFF did.
Update testsuite references
Merge Brecht's unassociated alpha fixes
Python overhaul: ImageInput (fixes, expose new methods, unit tests, docs)
Also many of the "global" functions and symbols have been overhauled.
Python overhaul: ImageOutput (fixes, expose new methods, unit tests, docs)
Rebuild PDF docs
Merge pull request #667 from lgritz/lg-python

Python overhaul: ImageInput & ImageOutput (fixes, expose new methods, unit tests, docs)
oiiotool --origin and --fullpixels did not correctly propagate their changes
to the underlying ImageBuf's spec as well as the copy in the ImageRec.
But some other opertions would check the IB directly to determine iteration
ranges. So if you were operating on an image that was a crop window (i.e.,
different display and pixel windows), and did an --origin (or --fullpixels)
followed by another operation that used the IB's range directly, you could
end up with strangely offset results.
Fix ImageBufAlgo::colorconvert - no-op color transformations broken.
It incorrectly took an early out for NoOp color conversions, leaving
the destination image having undefined pixel values.

Bug fix suggested by Esteban Tovagliari.
DPX bug fixes:

DPX output fix: incorrect addressing when writing crop images
DPX input fix: was not picking up offset or originalsize
oiiotool --fit fixes:
* wasn't modifying spec offsets properly
* wasn't padding correctly for --fit:pad=1
Modifications to range compression/expansion.

The coefficients we use to do range compression turn out not to work
well in practice, nor does it match the old tool we use at SPI that
oiiotool is replacing.  Actually, I was unintentionally given
sub-optimal values when I first implemented it in OIIO, when better ones
were being used elsewhere but we didn't realize there were two sets
floating around, oops.

An intersting consequence is that the old coefficients did not alter
values <= 1, so a LDR image would by definition not need the
transformation applied.  The better coefficients, unfortunately, do
compress the range even for values < 1, which is unfortunate, but at the
end of the day the new coefficients do a better job of the intended
purpose.

This patch:

* Alters the coefficients used for the logarithmic<->linear
  transformation used by IBA::rangecompress / rangeexpand.  These work
  better in practice.

* The docs have been altered to no longer say explicitly that values
  < 1 are unchanged, nor that it's a no-op for LDR image formats.

* Remove various code shortcuts that avoided the transformation for LDR
  images or values < 1.  Gotta do it all the time for results to match
  correctly.

* Changes the default for rangecompress/expand to transform each color
  channel independently, rather than use the luma.  The option is still
  there, we're just changing the default to the one that years of
  experience at SPI was preferred.  This applies both to the IBA functions
  themselves, as well as the commands in oiiotool.

Please note that this also applies to the behavior of maketx when
the --hicomp option.
Fix DPX test output to insulate it from version numbers in the iinfo
Git rid of the 'NEW' designation in docs for things that are no longer new.
CHANGES, docs fixes
Rebuild PDF docs
Bump version for 1.3.3