Cubical

Re-release of `v1.6.3` due to error in wheel upload.

Minor fixes which allow parallactic angles to be applied without specifying a model.

- Adds heterogeneous beams support for degridder-based predict
- Reverts regions parser to deprecated DS9Parser due to the new parsing within regions 0.5 silently failing to open some valid regions files.

Minor version release to fix the following
- Workaround for Numba bug affecting versions available for Python 3.6 that fail to detect TBB correctly. In such instances the number of threads per chunk is dropped to 1
- Cleans up derotation logging
- Fixes bug in solver warning in logging in low snr/no solutions case
- Fixes narrow-field bug when applying beam solutions in predicting from intrinsic models far off the phase center, especially evident for near-polar observations
- Support DicoModels formed by rephasing (e.g. mosaicing)

Python2 has been laid to rest.

Checkpoint release prior to PyPI upload and merge of ragged SPW support.