Addition of application-level power profiling support in NRM

An application-level power profiling support is added the NRM to report application run power/energy profiles. This is required to assess the effectiveness and impact of power policies currently in NRM and that will be added in the future. A very basic solution using SensorManager is implemented to measure the initial and final values. The difference in values can be reported as a part of the application 'exit' event. This does not handle multiple containers/applications and will have to be fixed in the future.

Closes #12 (closed)