These changes just make the errors, success messages, and informational messages look more user-friendly and make them easier to understand for newer users of the plugin.
Also removes some of the 'slang' messages and replaces them with more professional ones.
When running any zNPCsPlus command in console, it throws an exception stating that the command could not be run.
This adds a check making sure that only players can run zNPCs related commands to avoid the thrown exception.