Refactor all color management code into class + module

Because we'll need to be applying color transformations to a number of
different objects (internal DIBs and layers, VB forms and picture boxes,
etc), it made sense to abstract a number of color management functions
into a standalone module.  The old pdICCProfile class now wraps these
functions, and the new ColorManagement module provides an excellent,
highly portable solution for coders who want to integrate color
management into their own application.
Turn on color management for image layer DCs
When PD is first loaded, cache the path of the active desktop ICC profile

Interestingly, when assigning color profiles to DCs, we cannot use
internal Windows color profile handles - we can only use filenames!
Seems a bit bizarre to me, but oh well.  This commit includes code to
retrieve the filename to the current system color profile, which PD
calls early in its loading process.