add tests & fixes

[casperdcl]

• [x] add amyloid pipeline tests
  • [x] histogramming
  • [ ] basic_recon <- was passing, now failing after updated scatter method; needs new Zenodo reference data
  • [ ] align_mumap[spm] <- failing due to wrong mumap dims
  • [ ] align_mumap[niftyreg] <- failing due to wrong mumap dims
• [x] improve pytest framework
• [x] add cloud testing
• [x] add coverage reporting
• [x] fix CMake warnings
• [x] fix multi-array npy => npz
• [x] replace deprecated nii.get_data => nii.get_fdata
• [x] misc build & packaging improvements
• [x] misc formatting improvements

How to run tests:

• Ab_PET_mMR_test should exist in either $HOME or $DATA_ROOT

git checkout test
pip install -e .[dev]
pytest
pytest -k "align"  # only tests with "align" in the name