New version of GOLEM

[ajacquey]

Here is a list of improvements - new features which could the topic of a new GOLEM release version:

• [ ] Improve memory usage for the mechanics
• [ ] Direct solve for the plastic update
• [ ] Direct solve for Maxwell viscoelasticity
• [ ] Advection based on the entropy-production viscosity formulation
• [ ] Aperture update based on normal and shear stress on fault plane (Hannes)
• [ ] Reorganization of the materials
• [ ] Use automatic differentiation