Adds the govdelivery_signup and govdelivery_taxonomy modules. This branch will also switch from using GovDelivery's deprecated SOAP API to a newer RESTful API.
- Changes
* Use Libraries API
* Issue #1614422 by John Franklin: invert the count clicks permission
* Issue #231228: Replace "scope" with blocks-like visibility.
- Bugs
* Issue #1179408: incompatibility with clean urls disabled.