Treat more things as first-class resources

[grzleadams]

IIRC a lot of resources are lumped in with their parent resource (i.e., "notes", "email notes", "education", are not resources themselves, but are included in greenhouse_candidate). We should really strive to treat as many things as possible as first-class resources.

[grzleadams]

Note that this would also probably clean up the logic significantly; instead of looking through the parent object's list of notes, for example, to see what changed, we could simply respond to changes in the resource itself.