nova: support to get consumed time of a thread

Issue #813
add tool to gather cpu utilization of threads

* wrap CPU interface
* add cpu_monitor interface
* add test client using cpu_monitor interface
* support for FOC and NOVA

Issue #813
foc: add support to get cpu idle times of kernel

Issue #813
nova: add support to get cpu idle times of kernel

Issue #813
cpu_monitor: provide cpu idle times

works for foc and nova

Fixes #813