Orthogonal views

[AnniekStok]

Proposed Change

Add additional viewer models to view the orthogonal views (xz, yz) of the same data.
All interactive functionality (painting, selecting nodes, changing tool modes, undo/redo) should sync between the different viewers.

Checklist

• I have added tests that prove that my feature works in various situations or tests the bugfix (if applicable).
• I have checked that the tests pass and I maintained or improved test coverage (if applicable).
• I have written docstrings and checked that they render correctly in the documentation build.

Further Comments

• How to best extend/change this in order to also allow viewing different data (e.g. reference data) or the same data but at t+1? How can we best give the user more freedom about what to display in the different viewer models?
• If the content of the different viewer models diverges from the main viewer, we will need separate Qt layer controls per layer per viewing model. Right now we only have the Qt layer controls of the layer on the main viewer, and sync the properties such as 'mode' and 'n_edit_dimensions'.
• Currently the different viewer models are not dockable (though the window can optionally be hidden/resized). Trying to undock the entire widget kills the application for unclear reasons if it contains any viewer models :(