Command hooks: stage 2.

The second half of command hooks:
- Dynamically registered hook exceptions are provided, by fetching a hooks skip rules file
  from a URL.
- Hooks are loaded and activated by the noun/verb framework.
- Hook selection and dispatch has been substantially updated.

Also did some long overdue cleanup of string quoting consistency.

Bugs closed: aurora-270

Reviewed at https://reviews.apache.org/r/20928/