[Core] Add interceptors for Attributes

[yuripourre]

I have no idea how heavy it will be but we need a way to be updated if a certain concept gets updated.

Concepts could have a list of listeners (can be empty) that are updated/called when there is a change.

[yuripourre]

The problem with the suggested approach is that each null listener requires 4 bytes of memory.

One alternative is to keep the knowledge base immutable, add the interceptors to the knowledge base and everytime a concept is queried by the knowledge base it is wrapped in a way that those trackers are enabled.

The wrappers will have all the copied data from Concept and update the real data after changes.

[yuripourre]

Another way to do it is to only update concepts through the Knowledge Base.