[RFC] support for role names as the process_space in Looks

[KevinJW]

Recently I've been thinking a bit about how to improve the config format, so I'm going to open a few issues to spawn some discussions, relates to the recent v2 working group meeting discussion.

One thing I noticed this morning, is that it is not possible in v1 to use a role name for the process_space in a Look (running ociocheck fails as an example).

My specific use case was I wanted to specify in a generic way that client supplied LUTs 'client Look' should be applied in 'the client Look colour space', using the role as an indirection layer, which also helps with anybody reading the config, with understanding the intent.

I know there are limitations with this, when you have a requirement for multiple colour spaces, but I had another thought for that...

[remia]

Was just thinking about this again, it seems to be working on a OCIO v2.1 config I was testing, am I missing something or it always was working in v2?