Add support for configuring scheduled scan plans

Add support for configuring scheduled scan plans

Add the option to configure scheduled scan plans in the config file.
Each scan plan specifies the interval between scans and the number
of scan iterations. The last plan will run infinitely and thus
specifies only the interval between scan iterations.

usage:
sched_scan_plans=<interval:iterations> <interval2:iterations2> ... <interval>

Signed-off-by: Avraham Stern <avraham.stern@intel.com>