Clean up matroid constructor

[jdemeyer]

Some basic clean up of the matroid constructor. In particular, use normal variables like groundset instead of kwds['groundset']. Simplify the code and add more doctests for errors.

I'm particularly proud of this:

 2 files changed, 235 insertions(+), 256 deletions(-)

This is -21 lines despite adding several doctests.

Component: matroid theory

Author: Jeroen Demeyer

Branch/Commit: 23a7260

Reviewer: Stefan van Zwam

Issue created by migration from https://trac.sagemath.org/ticket/23382

[jdemeyer]

Branch: u/jdemeyer/clean_up_matroid_constructor

[jdemeyer]

Commit: 23a7260

[jdemeyer]

New commits:

23a7260

Clean up matroid constructor

[sagetrac-Stefan]

Reviewer: Stefan van Zwam

[sagetrac-Stefan]

comment:7

Clean code, all doctests pass. Nice work! It gets my positive review.

[vbraun]

Changed branch from u/jdemeyer/clean_up_matroid_constructor to 23a7260