add events to EconomyService for generalized events.

adjusted how withdrawal's and deposits are handled. Finalized many events so the implementation is consistent on how it handles economy interactions.  added onWithdraw and onDeposit so that the implementation isn't exposed in the API.

Signed-off-by: Nick Minkler <sleaker@gmail.com>
Merge pull request #525 from Sleaker/master

Events for EconomyService