Don't allow window move during keyboard detection

Previously, the user could drag the dialog title bar
(or hold the super key and drag anywhere on the dialog)
and move the entire initial setup window off-screen.

[endlessm/eos-shell#3425]
keyboard: move realize override into dialog class
keyboard: use a CSD titlebar and disable events on it

Since the FBE window is special, we can't let the right click menu show
up. Use the same technique we use for the main window.
Tabs to spaces

[endlessm/eos-shell#3425]
Merge pull request #74 from endlessm/shell/3425

Don't allow window move during keyboard detection