reduce brightness of VU meter backplate & increase contrast of peak-label
align gradient with meter-metrics
use only two colors for VU meter indicator and bright-gray for BBC
fix crash with "send" meters.

Meters in send-UI don't necessarily have a route,
but their type cannot be changed, anyway.
So just use "PeakMeter".
'overlay shadow' on meter-metrics experiment

TODO: shadow should really be 'behind'. ie save color,
stroke_preserve() shadow, paint text-layout with saved color
and eventually cairo_new_path() reset the path...
fix compiler warning
proper shadow for metric labels..
Merge remote-tracking branch 'origin/master' into clang