Restructure of grid creation code

[davidorme]

Description

This PR refactors the grid code for three main reasons:

• Removing the dependency on fiona - while excellent, the conda dependent install for this is too high a cost. The Shapely package loses some IO options for a wide range of GIS formats but provides extensive geometry operations.
• Establishing GRID_REGISTRY and a decorator to populate it: a user extendable dictionary of grid layouts.
• Provide a better signature for the main Grid (was CoreGrid) class that exposes the actual arguments and not a single config object.

The changes also then updates the existing test_grid.py to use the new structure, including moving imports outside of test functions. pyproject.toml and poetry.lock are updated to replace fiona (and tidy up a few misplaced / extraneous dev dependencies).

Fixes #28

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• All tests pass: $ poetry run pytest

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov-commenter]

Codecov Report

Merging #69 (4a16662) into develop (d879d33) will decrease coverage by 6.81%.
The diff coverage is 68.83%.

@@             Coverage Diff             @@
##           develop      #69      +/-   ##
===========================================
- Coverage    75.86%   69.04%   -6.82%     
===========================================
  Files            3        3              
  Lines           58       84      +26     
===========================================
+ Hits            44       58      +14     
- Misses          14       26      +12     

Impacted Files	Coverage Δ
virtual_rainforest/core/grid.py	68.75% <68.83%> (-7.18%)	⬇️

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[vgro]

Thanks for the update David. A few comments:

• great that you found a way to work around fiona, this will make it easier for windows user
• I am not sure what the advantage of the grid registry and the decorator is compared to the previous approach, I personally find it easier to understand how things are nested by using the dot operator. Apart from that, it looks correct as far as I can tell
• I like the way you changed the Grid object, it is much more intuitive now (without the config)
  From my side it looks all good, I think it would be good to wait for the experts' comments before merging :-)

[davidorme]

@vgro The main advantage of the registry is that users can extend the set of grids. They could write:

@register_grid('lspace')
def make_l_shaped_grid(...):

Honestly, once we've got the three regular polygons that tesselate, it isn't obvious what the use case would be, although I can sort of imagine a situation where someone uses an irregular polygon map. We might want to keep in mind use cases with focal areas of differing size and shape?

[dalonsoa]

I have requested a few changes and made a couple of comments, but otherwise I think it looks cleaner and way easier to maintain and test than having an if statement with several branches.

[dalonsoa]

All looks good to me, now!