Handle configuration and paths in a standalone way

Also, abstracts QSettings under LeapSettings and adds a way to define
the VPN env in a platform dependant way.
Add changes file
Fixes as per review
Wrap bool setting casting in a method
Add Windows prefixer
Add Windows VPN Launcher
Alias cp65001 to utf-8 for Windows
Make Windows use a regular socket
Calculate mtime in a more multiplatform way
Add changes file