misc Devices list and menu changes

Devices menu activate Open on left-click
Devices menu activate Remove / Eject on middle-click
Devices menu add Mount and Unmount
device remove via desktop shows progress dialog
fm Devices menu show and obey option Settings|New Tab
allow HAL eject unmounted
add HAL unmount optical in addition to eject
fix HAL duplicate devices listed
Devices list and menu Mount and Unmount sensitivity