Attached patch adds support for passing tables as matrices (or vector)
to a Calc source block through the :var parameter.  There might be a
better way to do it than manually construct the data structure expected
by Calc for a matrix but given that it rarely sees changes in this area,
it shouldn't be a bother.
I also added tests for this feature, and other simple tests to ensure
everything works.  I checked that all the tests passed on my side.