Pin py-torch to 1.9.1

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!83

(due to a known build fail of 1.10.x → to be investigated later)

Cleanup and fix py-torch concretization

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!82

Dependency on py-pybind11 now "open" interval… (i.e. later than 2.6.2
allowed for newer version of pytorch).

Previously, we had compiler and python mentioned as specs and relied
on "together" concretization to pin the dependencies. Now, we provide
these constraints via "packages" section, providing global constraints.
Site-specific things, like "mpi" provider/external libs, or architecture
"target" constraints would also go in there…

new NMPI Client release

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!78

Add missing dependencies for LFPy. Version 2.2.3->2.2.6

Closes #11

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!77

See MR !75 from Eric Muller

resolve conflicts for MR#61