Align the setting and passing of bounds

[NicolaCourtier]

We should perform a thorough check of everywhere bounds are passed, add tests for different formats and update the documentation. The application of the bounds in BaseOptimiser was changed in #661 and not all bases were covered. Things to consider:

• bounds in different formats e.g. lists and dictionaries
• inappropriate formats such as strings
• one-sided bounds
• infinite bounds, including transformed bounds e.g. log(0)
• when to remove bounds e.g. via the input bounds=None
• bounds for plotting