Issue 939 sim defaults

[valentinsulzer]

Description

• Add default parameter values, etc to the base model
• Copy attributes before assigning them to the simulation to avoid them changing unexpectedly
• Remove the C-rate parameter, except for using via the simulation

Fixes #939

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 #952 into develop will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #952      +/-   ##
===========================================
+ Coverage    98.06%   98.08%   +0.02%     
===========================================
  Files          220      220              
  Lines        11370    11361       -9     
===========================================
- Hits         11150    11144       -6     
+ Misses         220      217       -3     

Impacted Files	Coverage Δ
pybamm/models/base_model.py	98.63% <100.00%> (+0.04%)	⬆️
pybamm/parameters/parameter_values.py	99.08% <100.00%> (-0.15%)	⬇️
pybamm/parameters/print_parameters.py	97.14% <100.00%> (+0.17%)	⬆️
pybamm/simulation.py	98.41% <100.00%> (+1.36%)	⬆️
pybamm/solvers/base_solver.py	99.48% <100.00%> (+<0.01%)	⬆️

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[brosaplanella]

Looks good to me, thanks!