Adding BoxManagerOptions enum

These are options to customize the behavior of the BoxManager.  The only
option curently is to 'RetryRequestWhenHttp500Received'.  This is added
to try to smooth out the client behavior a bit when things go wrong with
the request for server-side reasons.
Increasing the test wait time to let Box catch up.
Optional one-time retry of sync. requests

If a synchronous request gets a 500 error (or something happens at the
transport level) then it can now optionally be retried once.
Changed enum name for clarity
Added one second wait before retrying request