Synchronize display off transitions with lipstick

When turning display off, mce gives lipstick time to finish rendering
before putting the frame buffer to sleep via early/late suspend.

When turning display on, mce tells lipstick when frame buffer is
is resumed and ready for use again.

[mce] Synchronize display off transitions with lipstick
Clarify handling of replies to setUpdatesEnabled() dbus method calls
Merge pull request #63 from spiiroin/synchronized_display_off

Synchronize display off transitions with lipstick