Several fixes regarding renaming

OK, we need to fix the documentation for `UsedNicName`, which says only "# Checks if given nic name is used already."
Also `GetNetcardNames` says "# Creates list of names of all known netcards". What if I have a configuration for a card that no longer exists, that was removed? Is it included? Does the comment need clarification?
(Another method, which is used in `edit_nic_name_test.rb`, is `getNetworkInterfaces`, with "# get list of all configurations for "netcard" macro in NetworkInterfaces module". Funny thing, `UsedNicName` does not use it.)