Implement New Permissions Per Updated Google Doc

* Removing has_and_belongs_to_many relationship between users and roles, and replacing with a one-to-many relationship.
* Adding read_only role to main seed file. Will need to run db:seed task to add it to staging and production
* Adding migration to handle removing CSR role, adding read_only role, and migrating existing users from the former to the latter
* Updating ability file to match ability matrix document
* Adding open capacity ability tests
* Adding provider ability tests
* Adding provider relationship ability tests
* Adding services ability tests
* Adding empty test for service request abilities
* Adding trip claim ability tests
* Adding empty test for trip results abilities
* Adding trip ticket ability tests
* Adding trip ticket comment ability tests
* Adding empty test for waypoint abilities
* Adding user ability tests
* Removing old combined ability test
* Reorganizing abilities to accommodate more restrictive site_admin permissions
Merge branch '1267-implement-new-permissions-per-updated-google-doc'

Conflicts:
	app/models/ability.rb
	test/unit/ability_test.rb