Polishing a few rough edges:
* Enable scrolling on the Plugin List view. It only fit 6 or 7. I have 13.
* I fiddled a bit with column auto-sizing (left it commented out, see comment).
* A whole bunch of tweaks to the settings view:
* first row of controls was cut off at the top (under the window title bar)
* fixing that revealed uneven spacing between columns
* action buttons were teensy tiny and unreadable
* settings view columns were too narrow (200 px).
* added some spacing to help with readability
* settings windows now start in center of current screen rather than some random place.
