`HCcoordnames=[], HCidnames=[]` is longer accepted as valid by
python-casacore and casacore.

Now that python-casacore can create a proper MeasurementSet, we no
longer need to rely on our own definition of it and it's subtables.
However, do create custom tiled arrays and hypercolumns for
DATA, MODEL_DATA, CORRECTED_DATA, FLAGS, FLAG, FLAG_CATEGORY,
WEIGHT, SIGMA and IMAGING_WEIGHT in the kat_ms_desc function.

Take averaging into account

This reverts commit 4f40f94.

They should vary by correlation, not channels.

Set up a Data Manager Info object with tile sizes specified for each
Data Storage Manager. kat_ms_desc_and_dminfo returns both a Table
Description and Data Manager info object suitable for passing to
create_ms.

https://casa.nrao.edu/Memos/229.html#SECTION000615000000000000000 says
that DIRECTION has shape (2,) and since every row in SOURCE table
corresponds to a FIELD, the extra dimension of size one seems
unnecessary.

Aim for 4MB tile chunks. Further customisation of the tile size is
possible.

Conflicts:
	scripts/h5toms.py

It automatically gets add in the C++ ms layer.
See casacore/python-casacore#72 (comment)
for more information.

…re-ms-creation