Pass arbitrary options to `axes` and `plot` functions via an option in `HybridPlotBuilder`

[pwintz]

There are numerous axes properties that users may want to set when using HybridPlotBuilder. We should allow them to set them by a syntax such as

HybridPlotBuilder().axesOptions('name1', 'value1','name2', 'value2').plotFlows(sol)

Similarly for plot and axis (and others?).

[pwintz]

To-do items before this is done:

• [x] Add examples to the documentation in HybridPlotBuilder_demo.
• [x] Add documentation comments to the start of each new public function.
• [x] Update auto-complete information.
• [x] Add unit tests.
• [x] Merge into dev branch.