Hide some objects from outline

[melsophos]

It would be great if it were possible to remove some objects types from the outline view. For example, I don't care to see all definitions of variables in Python (they can be accessed with the Symbols package easily) and they clamped the outline by making it very long.

[aminya]

For this, I am thinking of a checklist like Minimap's quick settings. A checklist that allows unselecting the type of objects you want to hide.

[melsophos]

I think this would be perfect.

[aminya]

Blocked by #89