Add a default field to OpTuple used when the right parameter is empty
IN: Unify types
Add a test case for IN
Fix the error message for IN
IN: Fix the test-case
Fix the name returned for arrays
Define always the same order for results
fix a typing bug in union-like operators
frontend support for Cast

I'm not fond of how the types are handled, by being always considered
nullable. We may need to have different ways to build types, one for
table descriptions and one for expression/views.
document casts
Fix the order in pa_macaque
Merge branch 'oasis'
Merge branch 'agg'
Merge branch 'in'
Really fix ordering in pa_macaque
Merge branch 'ordering'