Assorted small fixes

Sorry for a grab-all CL. This is an accumulated list of small fixes that I had sitting in a branch.

Mostly no-op changes. More visible ones are:

* Unify the main font sizes across the UI.
* Remove the unintended separator in the New Project dialog.
* Increase the minimum window size to fit all the toolbar elements (fixes #1308).
* Nudge the menu slightly to the left so it's not aflush with the right window edge.

TBR