Add the current local time as a property.

This adds a the property 'clock', which returns the current
local time as the string hh:mm.

Additionally the keybinding 'shift' + 'o' was added to displaying
the clock as '[hh:mm]' .
Add a clock OSD mode and append it to other modes.

This adds a simple clock as a fourth OSD option to display
the current local time and player status.

Additionally the clock is appended to the OSD progress info.