first stab to recover dump_dynamical_matrices in public branch

[mjv500]

grabbed handy tool from old develop branches. Moved to src, and incorporated in build_things

[flokno]

In order to merge to the public repository, the following things are needed:

• [x] a descriptive binary name
• [x] code documentation
• [x] a test for users to verify that the installation works as expected.

@OrbitalC is doing a very good job e.g. here: https://github.com/tdep-developers/tdep/pull/48

See also https://github.com/tdep-developers/tdep/blob/main/CONTRIBUTING.md

[mjv500]

As I understand, the code currently reads in the force constants and dumps to an Abinit DDB file. Would convert_forceconstant_to_abinit_ddb be a better name, in line with https://github.com/ollehellman/tdep-devel/tree/master/src/convert_abinit_ddb_to_forceconstant ?

name can stay unchanged - the idea is others beyond abinit may want their own export options, and the infrastructure is there.

[flokno]

Merge @mjv500 ?

[mjv500]

hell yes!

[mjv500]

Thanks for the time and nagging flokno!

[flokno]

Maybe time for a 24.04 release ..