implement "quickbar" #73

Almost 7 years later, let me describe what I meant, since I never had the time to finish this

This is an ambitious feature, meant to make most larray features (and many other libraries in fact) available via the GUI.

Methods on an object can be chosen from a drop-down and then some kind of form is generated with all possible arguments of a function. Depending on the kind of argument (int, float, boolean, str, Array, Path, etc.) a different widget is used.

My proof-of-concept works by inspecting method signatures and docstrings to retrieve the arguments. Nowadays we could also use type hints/annotations.