Move call to schedule_maybe_produce_block into on_incoming_transaction_async to avoid double call of timer when in start_block. Updated new option descriptions.
Move call to schedule_maybe_produce_block into on_incoming_transaction_async to avoid double call of timer when in start_block. Updated new option descriptions.

EOSIO/eos,EOSIO/eos,EOSIO/eos,EOSIO/eos,EOSIO/eos