Reduce MATLAB boilerplate

[beddalumia]

We have a lot of boilerplate within matlab scripts and functions. We can indeed drastically reduce it by collecting all the elementary routines in suitable MATLAB packages, that will then become required dependencies for this repository.

Target repository for the new packages: https://github.com/bellomia/DMFT-LAB

[beddalumia]

Commit be9a12d adds DMFT-LAB to the requirements, and refers to it in several markdown files.

[beddalumia]

Commit bad4628 embeds DMFT-LAB as a git submodule.