Related #576 High/Low DPI Adapting

The Qt UI would change the size according to the logical DPI of the computer
Only Windows and Linux have been tested. (Should also work on Mac but have not tested).
The function is unfinished.
instead of importing this way you can import doing:

from freeseer.framework.dpi_adapt._qtgui import QSpacerItemWithDPI

I thnk it'll be more clean and this is how we are using Qt imports too with new files.

I feel like framework is also the wrong place to put dpi_adapt_qtgui since framework should be less Qt Dependent. A better place would be frontend.qtcommon which is where we put all the extra Qt related common files for Freeseer.