Add enlarged UI

[Gymnasiast]

The current interface is not really suitable for touch mode. This PR aims to make a start in supporting it.

Two things are changed in this PR:

• Dropdowns have more vertical space, so the user can choose more easily
• Dropdowns will always stay open on click, rather than requiring a drag action

Future additions will include drawing other widgets bigger, like the close button, price widgets, etc.

[AaronVanGeffen]

The added spacing will be a marked improvement for touch users, no doubt. I wish we wouldn't be increasing the height of separator items as well, but I can see why that's troublesome given the current widget system.

Ideally, future changes in window layout to accommodate this touch mode would tie in with refactors to the window system to make the layout more heuristics-based.

Testing this PR, one thing in particular stood out. When the window isn't large enough to accommodate particular dropdowns, it would be good to automatically spread the items across two columns. Initially, I thought this might be relatively niche, but the View menu makes it obvious what I mean, I think:

[Gymnasiast]