Issue 697 abs tol vec

[Scottmar93]

Description

Added setting tols by variable to the KLU solver.

Fixes #697

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.

• 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 #700 into master will decrease coverage by 0.09%.
The diff coverage is 66.66%.

@@            Coverage Diff            @@
##           master     #700     +/-   ##
=========================================
- Coverage   98.26%   98.17%   -0.1%     
=========================================
  Files         176      176             
  Lines        9106     9133     +27     
=========================================
+ Hits         8948     8966     +18     
- Misses        158      167      +9

Impacted Files	Coverage Δ
pybamm/solvers/idaklu_solver.py	82.29% <66.66%> (-6.12%)	⬇️

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[valentinsulzer]

Cheers @Scottmar93 , looks good, other than the coverage 😉

[valentinsulzer]

make it clear in the name that this function also changes self._atol. In fact this could all go in @atol.setter, either for KLU or BaseSolver