Access token is always supplied by the RequestManager

The BeeSwift RequestManager adds authentication information to all requests. However, in the past this would not work in some scenarios, for example when code is running from extensions. To work around this some actions would also explicitly add the access token to the URL.

RequestManager should now always add the credentials (as they are stored in a location shared with the app group) and so this should no longer be necessary. Remove all locations in the code base where we manually passed through credentials to simplify the code, and reduce the chance of them ending up in logs.

Testing:

[x] Verify you can still add and refresh in the today extension
[x] Verify you can still add data through shortcuts
[x] Verify modified endpoints in the main beeswift app still work

beeminder / BeeSwift

Access token is always supplied by the RequestManager #395