<application.rb> Add feature to carts to handle wildcard ENV variable subscriptions

https://trello.com/c/B0BXoIjK/160-5-option-to-get-all-published-env-vars-carteco

 * Created new method - ```subscription_filter``` - to resolve
   subscriptions for ```component_instances``` without altering the
   cartridge objects themselves. This method
   handles "traditional" environment variable subscription
   and "wildcard" ```ENV:*``` subscription.

 * Added logic to elaborate method to consume new subscriptions
   array

 * Updated carts to use new wildcard environment variable
   subscription where appropriate

 * Added tests to verify both wildcard and traditional
   subscription specification in cart manifest is handled
   properly

 * Added logic to ```cart_repo_helper.rb``` to clean up both ```mock``` and
   ```mock-plugin``` carts

 * Added two unit tests to exercise ```elaborate()``` and
   ```subscription_filter()``` for cases where environment variables are
   subscribed to via "```ENV:*```" and where they are subscribed via
   connection type specification
   (i.e. "```ENV:NET_TCP:db:connection-info```")