Split ac-local into sub-libraries

[iboB]

• ac-local-core - core model, instance...
• ac-local-plugin - plugin utilities not needed by clients
• ac-local - client code with additional features which aren't needed by plugins, such as lib, scorers, etc

Not sure if this will be ever needed for anything besides interface purity.

A potential need (maybe in the distant future) would be to detach the versions of the three libraries and allow loading of plugins only based off of their ac-local-core version. Thus client versions can grow quicker and plugins won't need to be updated because of this