UNION queries fail

[iguberman]

Repo.paginate(query, pagination_params) fails with the following error:

 ** (Postgrex.Error) ERROR 42601 (syntax_error) each UNION query must have the same number of columns
     
         query: SELECT count('*') FROM ....  (any UNION query here)

This happens to a large variety of UNION queries. I'll provide some examples if necessary but I don't think it matters what specific query, it's just UNION queries in general. Probably need similar aggregate treatment asgroup_bys

I'm submitting this issue while attempting a fix on my end in the meanwhile.

[cpjolicoeur]

[fixed by #98]