Found issues with missing library files while testing on a clean system running
Ubuntu 19.04 that doesn't have the Qt library development packages installed.
However, even with libqxcb.so and libQt5XcbQpa.so added to install directory,
the client still would not start complaining about mixed Qt library versions. I
then finally decided to build the client on the debian official Qt5.7.1 package,
added libQt5DBus.so, libGL.so, libpcre16.so, all plugins in xcbglintegrations
and that worked.
The build script will now get the Qt bin directory via 'qtpaths' if not given.
Moved the LICENSE.md file to the root directory so github can now read it.
