I would prefer this to be called 'vcloud_gateway_interface_by_id' rather than get_gateway_interface_by_id.

The reasoning behind this is:

* We are returning a raw vcloud/fog hash structure. We should highlight this to the user (in the same way that we do with 'vcloud_attributes').
* We are trying to avoid 'get_' prefixes to methods, if i understand the get_by_name issues correctly.