Currently the build without implicitly included precompiled header
is not supported anyway (because Qt MOC source files do not include
stdafx.h, they include plain headers).
So when we decide to support building without implicitly included
precompiled headers we'll have to fix all the headers anyway.
Also fixed drag-n-drop images from Firefox in Windows.
Also some additional colors added to themes palette:
HistoryToDown button now has separate colors.
Windows title bar and buttons have separate active/inactive colors.
