[Feature] Selection of nodes and connections combined

[jpk6789]

Is your feature request related to a problem? Please describe.
Currently, the selection of nodes and connections are treated as totally different processes. While this may have its use cases, I would prefer, that selecting a node deselects all connections and vice versa. Of course, if I press the shift or control key, I expect the current behavior of selecting multiple ones (nodes and connections).

Describe the solution you'd like
It would be nice, if there is at least an option to toggle between the current behavior and the described one here.

Describe alternatives you've considered
I would not change the default behavior as it would change the behavior of existing implementations.

[miroiu]

The behavior you described is actually the intended functionality. If treating node and connection selection as separate processes is needed, I believe that should be implemented as an optional feature controlled by a flag.

[miroiu]

I merged the PR, but there are some improvements I will need to address in the future:

• unify selection events (good for undo/redo) [Bug] Unify selection events #191
• support selection previewing for connections (currently containers will be visually deselected when starting to select using BeginSelecting, but connections will remain selected until the selection is completed using EndSelecting even if EnableRealtimeSelection is true) [Bug] Connections are not visually deselected when starting a selection #192