(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.
The first argument to this method is intended to give the user an indication of the variable they need to supply. Instead of or in addition to "PE version," I would suggest including the exact variable the user should supply and how, e.g., "ENV['PE_VER'] (e.g., 3.4)"