Configurable namespaced inputs

This is continuation of #1043

* it simplifies defining input/action namespaces of form builder

Extracted custom namespace fix to #1065 

I have no idea why it is red, but will check it later.
When you create custom actions.  See the test in https://github.com/mikz/formtastic/commit/d41d05c0d11e4cbf5d186977f0d39916b579d9dd