chat: Send feedback when player is not authroized to use command.

- Feedback should be sent through SendMessage as ErrorMsg is
  not in the library anymore.
server: Modify verification functions to take objects not cdkey strings.
constants: Modify Register function

- Add extract parameter so that constants names can
  be used to string.match to extract the constant name
  from the 2da constant name.  This is useful when a
  constant has a prefix like FEAT_ that is unnessarily
  verbose.