Move "Apply" button for autoselection down a block and center it

[fedarko]

This would make it stand out to the eye more than it currently does, and would help users avoid confusing it with the Apply Filtering button. This would also have the nice side effect of enabling us to add on a tooltip for the Apply button -- the autoselection tooltip is really long, so there is probably a good way of splitting that text up between the two tooltips. (We could even rename this button to Apply Autoselection or something to make it extra clear.)

Based on discussion with @mestaki.