CloudApiClient tweaks and more unit tests (up to 85% coverage)

* CloudApiClient environmentDatabase(s) methods now return Cloud\Response\Database(s) instead of arrays
* Cleaned up some comments in CloudApiClient methods
* Adds several helper functions for building fake data
  * Should split these routines off into a separate class at some point
* Adds unit test coverage for the following CloudApiClient methods:
  * servers
  * server
  * siteDatabases
  * siteDatabase
  * environmentDatabases
  * environmentDatabase
  * databaseBackups
  * databaseBackup
  * createDatabaseBackup
  * taskInfo
* Adds tests to validate the URLs created are correct
  * There is probably a more succinct way of doing this than setting up a separate listener callback for each mock...