Implement battery and charger nyx-module

:Release Notes:
Implement and refactor the device module for battery
and charger nyx APIs

:Detailed Notes:
There is a device implementation of both battery and
charger modules. Since the sysfs paths vary on different
devices, sysfs paths are dynamically computed when device
is opened. The APIs implemented querying for battery and charger
status and being able to register for cllback when particular
events happen in the power_supply subsystem.

:Testing Performed:
Verified APIs with the following nyx-cmd calls:
nyx-cmd Battery readall status
nyx-cmd Battery readall ctia
nyx-cmd Battery register_status

nyx-cmd Charger query status
nyx-cmd Charger query event
nyx-cmd Charger register status
nyx-cmd Charger register state

:QA Notes:

:Issues Addressed:
[CTO-974] Implement battery and charger nyx-modules

Open-webOS-DCO-1.0-Signed-off-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>

Change-Id: I4588c5e61fa4193839661dbaa58e5bf1d162c78d
Reviewed-on: https://g2g.lgsvl.com/6518
Reviewed-by: DCO Verification
Tested-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Reviewed-by: Sapna Todwal <sapna.todwal@lge.com>
Reviewed-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Merge branch 'develop'