Removing the IsDocked property in upower

[Bastien Nocera]

Hey,

I've removed the IsDocked property in upower master (in preparation for
UPower 1.0). This property was supposed to be used to detect docks. Then
the usage changed slightly to detect whether an external display was
used. But it broke with hybrid graphics cards.

Instead of shipping with a property that's broken and lost its original
meaning, places where the policy is applied based on the presence of a
dock should be checking the presence of external displays directly with
the display server.

Not that this breaks the ABI if you used the IsDocked D-Bus property or
libupower-glib. A rebuild should be enough to fix that for the majority
of client applications.

Cheers