Integrate some common GLE matrices into ABIN

[danielhollas]

As suggested by Petr in a private email, it would be cool if we were not reliant on https://gle4md.org/ to get our GLE matrices, both in terms of safety in case the website goes down, and to improve user experience. It is also very easy to screw up units when downloading the matrices individually.

My plan would be to:

• Integrate some of the commonly used matrices for QT and PI+GLE (and perhaps PIGLET) directly into ABIN.
• Add a new input keyword omega_max or similar to indicate the maximum normal mode frequency in the simulated system. ABIN could then automatically decide which matrix to use.
• Add a new keyword to specify the type of simulation (QT, PIGLE, PIGLET etc).
• Obviously, we would still support reading the GLE-A/GLE-C files. (perhaps we need a new keyword to explicitly specify that the user wants to read these files?).

Currently, the downloaded matrices are specific to the given temperature, but I believe the values are actually linearly dependent, so we can just integrate a single matrix and then rescale it according to the temperature that user requested. This is another advantage of integrating the matrices.

Adding this to the (newly created v2.0 milestone.

@JanosJiri interested in your thoughts.

[JanosJiri]

That would be really good as automatic generation of the GLE matrices would simplify the workflow. Also, I've already seen some problems when people changed the temperature but forgot to change the GLE matrix, not knowing it matters. Having it all in ABIN would help avoiding these issues.