power_mgmt:sample:Power Manager application

Sample implementation of a power manager app that uses the zephyr
power management infrastructure. This app demonstrates use of the
hooks to implement Low Power State and Tickless idle power saving
policies.

Tested on quark_se.

Origin: Original
Change-Id: I10207014f2a844374b4c7a1c0ed50f2fb5c3c440
Signed-off-by: Ramesh Thomas <ramesh.thomas@intel.com>
Signed-off-by: Sergio Rodriguez <sergio.sf.rodriguez@intel.com>