Remove 'simplification' and other associated tests #1362

[asinghgaba]

Description

Removed Simplification class and relevant tests associated with it. Also, moved simplify_if_constant() to symbol.py.
Fixes #1362
Completed all the tasks specified in #1362

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 (not required)
• Tests added that prove fix is effective or that feature works (not required)

[valentinsulzer]

Thanks @asinghgaba! Just a couple of small things to change. Let's also wait to see if the coverage is still ok, I think it should be

[codecov]

Codecov Report

Merging #1369 (d8c0061) into develop (3851b18) will increase coverage by 0.07%.
The diff coverage is 85.00%.

@@             Coverage Diff             @@
##           develop    #1369      +/-   ##
===========================================
+ Coverage    98.13%   98.21%   +0.07%     
===========================================
  Files          277      276       -1     
  Lines        15959    15649     -310     
===========================================
- Hits         15661    15369     -292     
+ Misses         298      280      -18     

Impacted Files	Coverage Δ
pybamm/expression_tree/binary_operators.py	98.49% <ø> (-0.23%)	⬇️
pybamm/expression_tree/concatenations.py	97.60% <ø> (-0.17%)	⬇️
pybamm/expression_tree/unary_operators.py	99.79% <ø> (-0.21%)	⬇️
pybamm/models/base_model.py	99.10% <ø> (-0.01%)	⬇️
...m/models/full_battery_models/base_battery_model.py	99.68% <ø> (-0.01%)	⬇️
..._battery_models/lithium_ion/basic_dfn_half_cell.py	99.31% <ø> (-0.01%)	⬇️
pybamm/solvers/base_solver.py	99.12% <ø> (-0.02%)	⬇️
pybamm/expression_tree/symbol.py	97.49% <85.00%> (-0.75%)	⬇️
pybamm/expression_tree/functions.py	98.99% <0.00%> (-1.01%)	⬇️
pybamm/expression_tree/broadcasts.py	99.20% <0.00%> (-0.80%)	⬇️
... and 3 more

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[valentinsulzer]

It turns out there are a few more things to delete (from the coverage report):

• all the _unary_simplify functions
• all the _binary_simplify functions
• all the _concatenation_simplify functions

Then it should be done! There are some other coverage changes but each one requires different action so we can take care of later

[valentinsulzer]

all good, merging

[valentinsulzer]

@all-contributors add @asinghgaba for code

[allcontributors]

@tinosulzer

I've put up a pull request to add @asinghgaba! 🎉