Add BroadcastTime callbacks

:Release Notes:
Provide new API calls setBroadcastTime, getBroadcastTime and
getEffectiveBroadcastTime.

:Detailed Notes:
- callbacks for new API (see JSON schemas in code)
- first step on abstract away from NITZ toward Auto/Manual time
  settings
- user settings taken into account for getEffectiveBroadcastTime (note
  that time-zone set system-wide and thus system local time represents
  both user/auto timezone)

:Testing Performed:
Desktop build with appropriate luna-send

:Build Notes:
Depends on:
    https://g2g.palm.com/3594
    https://g2g.palm.com/3595

:QA Notes:

:Issues Addressed:
[GF-40247] Support API to send XDS time to luna-sysservice
[GF-40249] Provide API to obtain EBT from luna-sysservice

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Change-Id: If8cb1c8806a8e7ba869a3d80cb0d076efdb9a69f
Reviewed-on: https://g2g.palm.com/3596
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Build Verification