Issue 802 porosity

[valentinsulzer]

Description

Allow porosity to vary in space

Fixes #802

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• 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:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

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

[codecov]

Codecov Report

Merging #809 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #809   +/-   ##
=======================================
  Coverage   98.14%   98.14%           
=======================================
  Files         179      179           
  Lines        9919     9919           
=======================================
  Hits         9735     9735           
  Misses        184      184

Impacted Files	Coverage Δ
...amm/models/submodels/porosity/constant_porosity.py	100% <100%> (ø)	⬆️
...odels/full_battery_models/lithium_ion/basic_dfn.py	100% <100%> (ø)	⬆️
...bamm/parameters/standard_parameters_lithium_ion.py	100% <100%> (ø)	⬆️
pybamm/expression_tree/concatenations.py	97.98% <100%> (+0.02%)	⬆️

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[Scottmar93]

Looks good

[Scottmar93]

Sort of feel we should be defining these parameters inside the standard parameter file? Maybe that conflicts with the spatially dependent ones though...

[brosaplanella]

I agree with Scott. It would be good to pass it as a function or dataset, as with other parameters.

[valentinsulzer]

yeah, the problem is that param.epsilon_s now has domain "separator" and secondary domain "current collector", and so we would need to add "current collector" as a secondary domain to everything to avoid shape errors (tbh this should probably be automatic), and adding current collector to everything is unnecessarily complicated for this model