- an executemany() now requires that all bound parameter

- an executemany() now requires that all bound parameter
sets require that all keys are present which are
present in the first bound parameter set.  The structure
and behavior of an insert/update statement is very much
determined by the first parameter set, including which
defaults are going to fire off, and a minimum of
guesswork is performed with all the rest so that performance
is not impacted.  For this reason defaults would otherwise
silently "fail" for missing parameters, so this is now guarded
against. [ticket:1566]