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

Fixes: rhbz#886603

Change-Id: I1bb3486ed7168bda2855ee877e32423033620ecc
Raise NetworkError when ScriptRunner fails to connect.

Change-Id: I1d36685aa9b9035a8812908a60ad59a4d33de366
Fixes: rhbz#908838
Merge "Fail when Nova API, Nova network and Swift hosts are not set as IP addresses"
Merge "Raise NetworkError when ScriptRunner fails to connect."