Implement API for CBOX notifications

:Release Notes:
API requred to change dependency order between CBOX and DB8.

:Detailed Notes:
Implementation moved from MojDbMediaHandler to new 'registerMedia'
method on the private bus.

:Testing Performed:
tested on local build

:QA Notes:
luna-send -n 1 -a com.palm.configurator luna://com.palm.db/registerMedia '{"devices":
 [{"deviceId":"INTERNAL_STORAGE_DVR",
   "deviceName":"DVR_INTERNAL STORAGE",
   "deviceType":"internal dvr",
   "deviceUri":"/mnt/lg/appstore"},
  {"deviceId":"INTERNAL_STORAGE_CAMERA",
   "deviceName":"CAMERA_INTERNAL STORAGE",
   "deviceType":"internal camera",
   "deviceUri":"/mnt/lg/appstore/cam"}]}'

:Issues Addressed:
[BHV-3658] [DB8]: Implement API for CBOX notifications

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <igor.kuksiuk@lge.com>

Change-Id: I6169e2a776cf1ddeedc21bc4343a07cd5a85e254
Reviewed-on: https://g2g.palm.com/5308
Reviewed-by: DCO Verification
Reviewed-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Tested-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>
Reviewed-by: Oleg Yablokov <oleg.yablokov@lge.com>