add a "stop the movement" API call example

[Fil]

see https://bl.ocks.org/HarryStevens/8c9eba0905777a6ea778ebfc16f4d743

issue 1 is solved by adding if (inertia.timer) inertia.timer.stop();
http://blockbuilder.org/Fil/bf64676d0495518d98fffa21df46d0f0

[Fil]

issue 2 is more complicated, we need an API call to pilot the movement (with a possibility to call it in screen as well as in spherical coordinates)

[Fil]

ping @HarryStevens