Improve profile <-> air gap interaction

[reisecker]

It is now possible to reasonably work with the superposition view in conjunction with hiding the air gap: A set of profiles can be loaded. If they have surface markers toggling the air gap will also work in the superposed view. If not, the marker can be added via the toolbox and everything will update automatically.

However, there are places missing this interaction, e. g. the context menu to set markers and when deleting markers. In this case the files‘ inis must be saved and reloaded.

To solve this inconvenience a bit of a convolution in the old code needs to be untangled:

snowmicropyn/snowmicropyn/pyngui/sidebar.py

Line 161 in 780489c

# This is a bit tricky: We call the methods on main_window which

Since all code for this feature is probably going to be completely replaced in the future as issue #12 becomes more and more pressing for now this is as far as it reasonably goes - hopefully being resolved within issue #12.