Fail when Nova API, Nova network and Swift hosts are not set as IP addresses

- Refactor value validator system - cleanup, pep8, documentation, tests and allow multiple validators for each parameter

Change-Id: I69ac806d9efdb46196070d518d5ef5c5c174e6bb
Fixes: rhbz#886603
Merge "Fail when Nova API, Nova network and Swift hosts are not set as IP addresses" into folsom