quadray for subgroup of the ray class group

[Bill Allombert <allomber@math.u-bordeaux.fr>]

Hello PARI-dev,

I would like to compute Hilbert class field of non-maximal order.
This corresponds to a subgroup of the ray class group of the maximal
order. Is there any possibility to use quadray to compute defining 
polynomials for subgroups of the ray class group?

By the way, I think the documentation of quadclassunit should
enphasize it can handles non fundamental discriminants.

We should probably change rnfkummer to handle squarefree order.

Cheers,
Bill.