Major re-writing of Observers and Zarr Libraries :)

[yoctoyotta1024]

Major update to methods for writing out data to Xarray and aNetCDF compatible arrays in Zarr format:

• much less copying of data and more efficient copying via deep copies of arrays rather than element by element copies
• output in single precision (static casting) for most variables
• parallelisation of loops over gridboxes and superdroplets
• clearer distinction between Zarr and Xarray / NetCDF requirements
• less frequent writing of and more detailed metadata
• better consistency of metadata with chunking writing so output data can be viewed during runtime

• refactoring of the examples so that both the build stage and compilation of the executable are done in the bash script for each example and the Python scripts are for generating input files, running the executable and plotting the results.

:)