Rework calendar handling for time-based cols

Don't pass a null Calendar to ResultSet#get(Time|Date|Timestamp)
in underlying JDBC connection if no Calendar is available,
instead use the getXXX method that doesn't take a Calendar param.

This change also required a number of changes to the
OptiqAssert framework to allow supplying a Calendar to use when
checking query results, as it seems that the behavior of HSQLDB
is quite different when using ResultSet#getDate(i) and
ResultSet#getDate(i,null);