* Add `from_account` to notifications API

this adds the ability to filter notifications by the account they
originated from

* passing a non-existent user should cause none to be returned

* Fix codeclimate warnings

* fix more codeclimate warnings

* make requested changes:

* use account id instead of user@domain
* name the param `account_id` instead of `from_account`

* Don't use `return` in a lambda

Fix #340

* Add more granular OAuth scopes

* Add human-readable descriptions of the new scopes

* Ensure new scopes look good on the app UI

* Add tests

* Group scopes in screen and color-code dangerous ones

* Fix wrong extra scope

The spec was checking the activity_id of the activities held in notifications
within the controller.

Because the activities are different models, it is possible that they are
created with the same database IDs, and when they are this spec fails because an
activity which should not count as a match is counted as one.

* Add exclude_types param to /api/v1/notifications

* Exclude notification types in web UI through exclude_types in the API