Bug#884070: mention if no -g is given

[積丹尼 Dan Jacobson]

Package: electrum
Version: 2.9.3-1
Severity: wishlist
File: /usr/share/man/man1/electrum.1.gz

At
       -g GUI, --gui=GUI
              Select user interface, possible values are  qt, lite, gtk or text

Add:
        if no -g is used, electrum starts up in qt mode.