katello-configure - Include param name into wrong param error message

Compare:

     Option: [Katello user's password] not correctly specified.

with

     Option: [Katello user's password (--user_pass)] not correctly specified.
Non action method in controller should be private
Local variables snake_case instead of CamelCase
Use snake_case instead of camelCase for method names
Merge pull request #1671 from iNecas/kc-friendly

katello-configure - Include param name into wrong param error message
Merge pull request #1670 from iNecas/refactor

TDD: Refactorings