Save matrices and vectors on disk

[cedricchevalier19]

Being able to export matrices and vectors to file system is an important need for:

1. studying linear problem behavior
2. performing store/load of artifacts

We can use existing file format, such as MatrixMarket, Harwell-Boeing, ...
Or, we can design our own and provide converters. One way to do this should be to have a json output. Furthermore, we can have binary exactness using floating point literals, and small file sizes using file compression.

[cedricchevalier19]

This json output can be extended to handle meshes.

@arcaneframework/arcane-team

[cedricchevalier19]

Can solve #20

[cedricchevalier19]

Look at https://llnl-conduit.readthedocs.io