Windows Build fails to find needed dll because it builds in Debug mode

[MTRNord]

The current windows build done by appveyor makes a debug build and therefor misses these required files:

• Qt5Cored.dll
• Qt5Guid.dll
• Qt5Networkd.dll
• Qt5Svgd.dll
• Qt5Widgetsd.dll

A easy fix is to build a release version and use that as it than uses the correct and present dll files.

According to StackOverflow adding --config Release to the - cmake --build build line in the appveyor.yml file and changing the copy command to the release output folder would generate a correct release file and fix the dll loading bugs.

If wanted I add a PR (after nsis stuff is added or if wanted even in that PR) (Reason: don't want to mess that PR up :P)

[MTRNord]

#8 will fix this issue.