Add a number of standard keyboard shortcuts to menu items in the Qt UI,
especially under the File menu. To make action names more conventional,
rename "Create/Restore" to "New/Restore", "Copy" to "Save Copy", and
"Close" to "Quit". This also resolves the situation where
Create/Restore, Copy and Close all had "C" as their mnemonic.

Also allow fast switching between tabs by using Alt+[1-5], same as
in tabbed web browsers. Ctrl+PgUp/PgDown is still available.
network.pending_servers, to avoid connecting the same server multiple times
don't set network.interface to None when disconnetced
exit wait_until_connected() when all servers have been tried
fix typo
fix: pending_servers
Merge pull request #481 from haakonn/master

Improve keyboard usability in Qt GUI
add password to script
clarify text
installwizard: don't repeat same info
fix: return None if user presses cancel
fix issue occuring with set_server
partially revert code merged #481, brreaks old qt versions