display: Add init direction in rotation angle

display: Add init direction in rotation angle

init direction means the display direction of degree 0.
It is needed to know physical display state by app.

When deviced boot, it parses the conf file "/etc/deviced/display.conf"
and it saves the initial display is horizontal or vertical.

changed dbus method:
dbus_getrotationangle
  path: "/Org/Tizen/System/DeviceD/Display"
  interace: "org.tizen.system.deviced.display"
  member: "GetRotationAngle"
  paremeter: "(i)", display index to get rotation angle.
  return: "(iii)", 0 on success, negative on error.
	enum display rotation angle to get.
	enum display initial direction.

added configuration property:
  DisplayInitDirection : "horizontal" or "vertical"

Change-Id: I9a45d06b712a04d79e8614bac5880d4be6fe4fd3
Signed-off-by: TaeminYeom <taemin.yeom@samsung.com>