Add ability to set width of picklist widget and it's child dropdown/overlay independently

[atlanticaccent]

I'm not sure how feasible this is, but I think this would provide slightly nicer styling and allow the insertion of a much wider array of elements in the picklist. Alternatively, add automatic line breaks to elements in the dropdown, if possible, when the overall width of the widget is less than a given element.

An example of my current situation: What I'd prefer: What actually results:

[yusdacra]

This shouldn't be too hard to implement I believe. Changing this line to take the computed max_width (like here) should probably work.

[hecrj]

@yusdacra Would you like to make a PR?

[yusdacra]

@yusdacra Would you like to make a PR?

I have prepared a PR over at #993