Some cleanup in groups.<tab>

[nathanncohen]

Following the discussion at https://groups.google.com/d/msg/sage-devel/tyAxhqxk3ZI/SuBg2Ukwwj4J

I was about to say what this patch does, then noticed that it would naturally appear on the ticket as the commit messages of the new branch :-)

The reference manual page for groups looks like it could be reordered and made cleaner, but I know so few about groups that I am sure I would do it all wrong if I gave it a try ^^;

Nathann

CC: @vbraun @hivert @nthiery @videlec @jhpalmieri @kcrisman

Component: group theory

Author: Nathann Cohen

Branch/Commit: u/ncohen/15368 @ 0ad88a6

Reviewer: Volker Braun

Issue created by migration from https://trac.sagemath.org/ticket/15368

[nathanncohen]

Branch: u/ncohen/15368

[sagetrac-git]

Commit: 0ad88a6

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

[0ad88a6](https://github.com/sagemath/sagetrac-mirror/commit/0ad88a6)	Additions to groups.misc : AdditiveAbelian, Free, Braid, SemimonomialTransformation
[3d75bd3](https://github.com/sagemath/sagetrac-mirror/commit/3d75bd3)	Move QuaternionMatrixGroupGF3 from groups.misc to groups.matrix
[2a68051](https://github.com/sagemath/sagetrac-mirror/commit/2a68051)	Add affine groups to groups.
[017084f](https://github.com/sagemath/sagetrac-mirror/commit/017084f)	Broken link in groups catalog doc

[vbraun]

comment:3

Looks good to me.

[vbraun]

Reviewer: Volker Braun

[nathanncohen]

comment:4

Thaaaaaaaaaaaaanks !!!