This commit solves two interconneted issues. Wrong layouting when text is
printed and wrongly scaled fonts for printing. Device#getDPI returns values
for Display and Printer that lead to wrong assumption using getDPI e.g.
in the ScalingSWTFontRegistry. Printing text is broken because Printer
DPI (e.g. 600) is way different from the Monitor DPI (96) that lead to
inconsistent Font behavior in the different scenarios. Now font scaling
is utilizing the zoom level instead of DPI in relavant scenarios.