Add functions for comparing configs and color spaces

[doug-walker]

It would be very helpful to have some functions in the API that could be used for doing non-exact matching of configs and color spaces.

The config and color space classes contain quite a lot of data which does not affect the actual color processing, for example various description strings or optional metadata such as categories. So just doing a binary comparison of two objects, or comparison of the cacheID, only tells you that they differ in some way but not whether that difference is significant for your purpose.

The question of which differences are significant is highly dependent on the situation and does not have a specific definition. The proposal is that a function be created that would take a pair of objects and some way to identify what aspects of the object should be compared.