(CPR-63) Template mock configs

This commit adds in capabilities that check if a template for mock
configs are in place then creates the mock config from them. It then
uses the newly made mock configs in the usual method.
right, but if this conditional assignment assigns a value to `mockfile`, then down below you can check if `mockfile` has a value - if it does, you know you're building PE and can proceed without further assignments, and if not, the previously existing `mockfile` assignment on 266 will work.