Fixed TriviaTime.authweb().

- Replaced 'checkChannelCapability' with 'channel' from wrapper due to the
  existing (better) check within the method
Small change in TriviaTime.authweb().

- Set capability based on decreasing importance
Added custom capability checks. (issue #300)

- Added TriviaTime.isTriviaMod(), TriviaTime.isTriviaAdmin() and
  TriviaTime.getTriviaCapability() to allow better control over TriviaTime
  commands
- Updated TriviaTime.acceptdelete(), TriviaTime.acceptedit(),
  TriviaTime.acceptnew(), TriviaTime.add() and TriviaTime.authweb() to use
  the new capability checking methods