Allow template resource use outside of Environment

Allow template resource use outside of Environment

In addition to using TemplateResource as a means to override another Resource
implementation, this allows template authors to specify a template url
as the Type of resource directly. This allows a user to define new Resource
implementations in addition to overriding existing ones via Environments.

implements blueprint provider-resource

Change-Id: I11cf94dc062fcce0e4ff08765696447fc2411a7f