set bgcolor to gray in cropping dialog
set manual cropping if bbox exists
set widget spacing according to screen DPI
make larger default page margin
Merge pull request #771 from chrox/kopt-bbox-fix

set manual cropping if bbox exists in koptinterface
Merge pull request #772 from houqp/new_ui_houqp

fix whitespaces
record multiple slots for multi-touch input

for now, only slot 0 is parsed, the rest are ignored.