Added BarSize conversion from ib to QDMS.
Added another test for the HDB, ensuring exception is thrown when
requesting data from non-existent datasource.
Fixed a crash when trying to find an Instrument's Exchange's timezone,
when the exchange isn't set.
Used instrument's own timezone-finding method.
Wrote a couple of tests for Instrument.GetTZInfo().
Wrote a couple of tests on the IB historical request splitting
mechanism. Both pass.