SRADA-827 Added Screenshots support from Cli

SRADA-827 Added Screenshots support from Cli

 * Now it's possible to specify parameteres for screenshot period
   with -S or --screenshot <value>, where value is a positive integer number
   of seconds in period between screenshots. If empty or 0 then
   onSceneTransition option enables.
 * Added CliInternals.selectScreenshotFeature(..) that enables screenshot
   onSceneTransition or periodically.
 * In CliInternals.selectFeatures(..) simplified.

Change-Id: I3d3e514b30f3b09a073703554e7e2d0dda78bf24