Revert "Adding information about external templates in design.md"

This reverts commit 5b2731dbe2.

docs/design/design.md

@@ -155,12 +155,7 @@ passing configuration to Deployment Manager.
 
 ### Instantiating Templates
 Templates can be instantiated in the same way that a configurable resource is
-used. They can be used in two different ways, either passed to the API as an
-imported file, or used from a public HTTP endpoint.
-
-#### Imported Templates
-Templates may be imported as part of the target configuration and used
-directly, for example:
+used, but must be imported and included as part of the configuration.
 
 ```
 imports:
@@ -177,30 +172,6 @@ The _imports_ list is not understood by the Deployment Manager service, but is a
 directive to client-side tooling to specify what additional files should be
 included when passing a configuration to the API.
 
-Using the Deployment Manager API, these templates can be included in the
-imports section of the _targetConfig_.
-
-#### External Templates
-Templates may also be used from a public HTTP endpoint, for example:
-
-```
-resources:
-- name: example
-  type: https://raw.githubusercontent.com/example/example.py
-  properties:
-    prop1: prop-value
-```
-
-The service will process external templates as follows:
-
-1. fetch the external template as an import
-1. attempt to fetch the schema for the template, using
-  _<full template path>.schema_ as the schema path
-1. repeat for any sub-imports found in the schema file
-
-When fetching schema files and sub-imports, the base path of the external
-template is used for relative paths.
-
 ## API Model
 Deployment Manager exposes a set of RESTful collections over HTTP/JSON.