Added customtrigger(identifier) clue.

This clue type allows you an easy code-free way of creating your own events. Using the /cluescroll customtrigger (player) (identifier) [amount] command you can call for a clue to be marked. Amount is optional and wi

Example:
Have a customtrigger with identifier (voter). When your vote plugin executes vote rewards for a player, have it issue the command: /cluescroll customtrigger (player) voter 1 to update the player's clue.