OptimiseResult().__str__ across examples, adds OCP balancing script

[BradyPlanden]

Description

1. Instead of printing the optimisation result values, the OptimiseResult().__str__ is used which includes a better summary inclusive of the optimised values.
2. Adds a script for fitting the OCP stoichometry parameters for a single particle model from synthetic data.
3. Sets BaseOptimiser.verbose to default True. This only affects printing the OptimisationResults and the PintBaseOptimiser halt conditions.

Issue reference

Fixes # (issue-number)

Review

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.09%. Comparing base (c8b00e6) to head (c1e0e62).
Report is 5 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #536      +/-   ##
===========================================
+ Coverage    99.08%   99.09%   +0.01%     
===========================================
  Files           52       54       +2     
  Lines         3605     3764     +159     
===========================================
+ Hits          3572     3730     +158     
- Misses          33       34       +1     

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