Updated TriviaAdmin-only commands. (issue #300)

- Updated TriviaTime.clearpoints(), TriviaTime.givepoints() and
  TriviaTime.transferpoints() with new capability checking methods
Updated TriviaMod-only commands. (issue #300)

- Updated TriviaMod-only commands with the new capability checking methods
Minor change in TriviaTime.add().

- Changed it back to the old way of user checking since it wasn't an issue
  (same case as TriviaTime.addfile() with owner)