NiftyPET/NIMPA: nimpa v2.0.0 stable

• fix & upgrade logging
• fix & update dependencies
• add [plot] extra
• use AMYPAD/SPM12 for MATLAB engine & SPM12 support (#6)

Installation/build framework

• drop Python 2 compatibility
• support Python3.6+
  • drop py<=3.5 which are unsupported by ninst<-miutil[cuda]<-pynvml and no longer receive security fixes anyway
• fix conda install
• allow non-interactive installation (#1)
  • allow setting PATHTOOLS from env vars (#1)
• new build framework (#9, #11, #12)
  • cmake/cuda build overhaul
  • allows pip install nimpa on a completely clean system (no numpy, no miutil[cuda], no -e, no --no-binary :all:)
  • replace dinf module => miutil.cuinfo (#7)
  • rely on numpy, miutil[cuda], ninst, scikit-build, cmake>=3.18, ninja
    • all auto-installed at setup-time!
    • get rid of cudasetup.py
    • get rid of install_tools.py
    • get rid of resources.py
  • use new CMAKE_CUDA_ARCHITECTURES policy
  • use new project LANGUAGES specification
  • support python setup.py clean
• basic code tidy (particularly import ordering)
• update .gitignore, .mailmap, README.rst badges