Intialize new phosphor-time-manager

phosphor-time-manager will be refactored to use sdbusplus interfaces.
This is a initial commit that EpochBase is implemented based on dbus
interface xyz/openbmc_project/Time/EpochTime.interface.yaml.

EpochBase is the base class that wraps EpochTime interface, and is
initialized with time mode and owner from settingsd.

An initial unit test case is added.

Change-Id: Ic944b70f63ec3c0329762cc8874f0f57b09ddce3
Signed-off-by: Lei YU <mine260309@gmail.com>
7 files changed