v0.24.2 - the column under the header follows it down

Fixes a regression in v0.24.1.

v0.24.1 measured the title and fixed the title, then handed the problem to the
next control down. The gauge was allowed to move, but the boost slab under it
was still pinned at 108 - so on a 125% display the gauge came down to 76, ended
at 110, and sat on the blue.

Measuring one control in a pinned column does not work. The column is a column
now: the gauge follows the subtitle, the big buttons follow the gauge, and one
drop carries the four bands, the three centred lines, the two switches, the
sentry door and the console down with them. The window grows by exactly that
much, so the console keeps its height rather than paying for the header.

On a 125% display the drop is 11 and the window comes out 893. At 9pt on a 96dpi
screen it is 0, the window is 882, and every control lands on the pixel it was
pinned to.

Also: the boost slab reads "Kill the background junk."