Stubs for new functions
pulling in changes from pervious issue.

Merge branch 'develop' of https://github.com/locationlabs/confab into feature/ci170
Add support for including Dataloader callbacks by scope to import additional data.
 * Added new add_hook/remove_hook functions
 * Updated Dataloader.__call__ to call hooks during data load

CI-170
Added result caching per requirement.

CI-170
Updated with comments from SYS-201.

CI-170
Incorporated comments:
 * Added hook stuff to confab.api
 * Use local instance of HookRegistry to test add/remove
 * Added __eq__ to Hook class for easier removal

CI-170
Added a way to bypass hook processing for use in Elmer.

CI-170
Removed __eq__ operator of Hook class.
Updated documentation
Merge branch 'feature/ci170' into develop