Better class uid support in OASF API

[akijakya]

Currently there are a lot of API endpoints required to pass a name parameter, but in case of classes (skills, modules, domains) it only works with the class type name (e.g. text_completion instead of the "official", hierarchical name natural_language_processing/natural_language_generation/text_completion). It would also make sense to work with the id of the class.

I propose passing either name or id as optional parameters in the request.
In some cases, leaving these parameters blank would mean return all classes.