Moves imghash internals to sub package, so they can be
used in other tools.
Adds Distance function to imghash/lib.
This function computes the Hamming distance between two given
hashes.
Moves external resize package into imgscale/lib.
This is done to keep all the relevant code close together.
Removes dependency from main README and adds listing for
new imgindex command.
Modifies imghash/lib to refer to new location of resize package.
Adds file extension registration and verification code
to lib and its sub packages.

This allows tools to pass in file paths and verify if
they represent a known registered image format.
Makes the file format sub packages in lib/ part of lib itself.
This way any of the tools do not have to manually import the
file format subpackages themselves. This makes it easier to
add new filetypes as all the relevant code is now confined
to the lib package. Any tools using it, will then automatically
offer support for all relevant image formats.
Modifies existing tools to reflect last changes to lib package.
Begins work on imgindex tool.
Performs some minor refactoring.
Fixes imghash to use fastest scaling algorithm.
This is still terribly slow, but nothing we can do about that now.
Revises imgindex README.
Finalizes implementation of imgindex.
Removes imgindex tool. It is too simplistic to be useful and its
functionality is better created by shell scripts which use the
imghash tool, combined with logic which filters out images
that have not been changed since the last time the operation
was performed.