Added /covercharge, p. effect abilities use highest effect for your level, bug fixes

(Added) Entertainers can now add Cover Charges for their performance
(Feature) Using a performance effect that has multiple effect levels
will use the highest effect for the entertainers level
(Code) Added 2 new methods (Jython and Java version) for Input Boxes
that automatically adds the input text to return list.
(Code) Moved essential spectating code from /watch script to
startSpectating
(BugFix) Fixed Null Error when trying to cancel Experience tick if
leveled with a cheat.
(BugFix) Fixed system messages error on performance abilities