$qt_dir in the build script will now default to the hard coded standard
directory for Qt binaries '/usr/lib/x86_64-linux-gnu/qt5/bin' if a valid
path is not provided by the user. End users that have customized setups
of Qt might need to modify this script to make sure $qt_dir points to the
correct directory at all times.
Moved the LICENSE.md file to the root directory so github can read it.
