Clock drift for Cooja motes

[e120guru]

Working with TSCH (and other syncronized protocols) it's neat to be able to simulate clock drift to test stability and syncing.

To be able to do so, I would like to be able to have Cooja mote's timers to get a drift factor, for instance -100ppm, or +30ppm, or so.

I'm not so much interrested in the tollerance when it comes to code execution since the Cooja mote is not really true to reality in that sense anyway - but for the timers (rtimer most specifically).

[alexrayne]

try PR #51