A number of enhancements to scriblio-authority

* Creating core scriblio-authority class for multi-purpose/required methods for the plugin as a whole
* Adding an endpoint for retrieving authoritative terms
* Making the JS plugin more flexible to work with both front and backend implementations being as non-destructive as possible
* Style tweaks
Renaming scriblio-authority class
Merge pull request #20 from borkweb/front-end-scriblio-authority

A number of enhancements to scriblio-authority