trac #16817: OA for n=205,254,469,520,522,524,1262
trac #16846: a difference_matrices module
trac #16846: Remove obsolete functions
trac #16846: Broken doctests
trac #16817: docfix
trac #16846: Merge with updated #16817
trac #16846: review

- removed TD_6_12
- OA_7_39 -> DM_39_6_1
trac #16867: Merge 520+x OA constructors
Trac #16817: OA for n=205,254,469,520,522,524,1262

New OA !

Nathann

URL: http://trac.sagemath.org/16817
Reported by: ncohen
Ticket author(s): Nathann Cohen
Reviewer(s): Vincent Delecroix
Trac #16846: a difference_matrices module

This commit creates a `difference_matrices` module which does not do
much at the moment: it can creates DM for prime powers, and return DM
from the database.

In the database, however, a lot changes as many OA were actually
difference matrices. The constructors are turned into difference
matrices constructors, and `orthogonal_array` now calls
`difference_matrix` to get them.

All in all what this patch does is mostly code administration, but well,
that's the way to go ...

Quasi-difference matrices will be handled later as there are some
problems with them, in particular in the way `orthogonal_array` will
query the future `quasi_difference_matrix` constructor.

Nathann

URL: http://trac.sagemath.org/16846
Reported by: ncohen
Ticket author(s): Nathann Cohen
Reviewer(s): Vincent Delecroix
Trac #16867: Merge 520+x OA constructors

These 3 OA constructors all do the same thing. Their doc is the same,
their code is the same. Let's merge them all into one function !

URL: http://trac.sagemath.org/16867
Reported by: ncohen
Ticket author(s): Nathann Cohen
Reviewer(s): Vincent Delecroix