Added method for checking if order is not filled yet.
Added some UTs.
Changed retry policy to a wating loop until a message arrives. This
simplifies FSM context implementation. Now it is clear that an order was
submitted or rejected.
Redesign of retry policy and FSM context: Now, no execution path leads
to an order in state CREATED or OPENED when submit fails. Policy waits
until a message is received. Dukascopy will clarify if the user can
specify a timeout(goodTillTime is not applicable for BUY/SELL orders.)