break out relative number fields into separate file

[ncalexan]

This has been some time coming, but let's separate relative number fields from generic/absolute number fields now, while I'm looking at them.

Component: number theory

Keywords: relative number fields files

Issue created by migration from https://trac.sagemath.org/ticket/5066

[ncalexan]

comment:1

Attachment: trac_5066-relnf-file.patch.gz

Fails a doctest, to be addressed by patches to #1357 (which will depend on this)

[roed314]

comment:2

Looks good, assuming that the other patch you mentioned (which isn't #1357) gets in at the same time. The only change that needs to be made is in sage.rings.polynomials.polynomial_quotient_ring_element, changing number_field to number_field_rel a couple places.

[ncalexan]

comment:3

Patch should be at #1367, sorry. With #5066 and #1367, all doctests pass on sage.math.