Backend package updates

[phockett]

Rolling list of things to fix due to changes on back-end libraries:

• Numpy datatypes (numpy >= 1.20.0), see https://numpy.org/devdocs/release/1.20.0-notes.html#deprecations
• (June 2024 update): Numpy definitely working for v1.23, but v1.26 breaks something in epsproc.IO.dumpIdySegsParseX(), related to array size or ordering? Or use of np.unique() - basically miss cases with empty matrix elements.
• Xarray fix for Geom functions for >=0.15.0, see GeomFunc todo & tidy-up #26
  • UPDATE 25/07/24: currently running <=2022.3.0 as newer versions may break some calc routines, older version also failing for some IO.
  • GH CI now OK, but only for xr=2022.3.0, see Tests and CI #42 (comment)
• Seaborn >0.9.0 for lmPlot() compatibility, see lmPlot overloading labels #24
• (June 2024 update): Matplotlib<3.9, to avoid change in colormap schema which breaks old Seaborn code.

[phockett]

Xarray and Python version issues

Fixed in #51

OK for current Xarray version (v2022.03.0) and Python 3.9.

Didn't fix Numpy datatypes, but no longer throwing errors?