Added deletion of participants and initator to closePoll().

Note: This breaks the tests because currently closePoll is automatically
triggered by checkPollOngoing. Need to seperate the two functions.
Seperated initiator and participant deletion from closePoll()
Removed closing of poll upon recieving all votes.

That wouldn't have made sense because people might want to change
their vote up to the last minute. If the poll is going to close early,
it must be done manually by the initiator.