Special data sending mode

[MadejaMaciej]

In addition to #16 please implement a special data sending mode -- when a change occurs.

For example, a device is resting on a shelf and it will not report gyro data even for hours or for the whole night. Because, since it is not moving at all (only one axis may change slightly, due to changing measurements of gravity) so there is no change in gyro data and there is nothing to be reported at all.

When device is configured and running in this special mode and is not sending data due to given data set is not changing at all in given period, is still must send heartbeat signals (#21) or regular basis.

[MadejaMaciej]

każdy (w trybie specjalnym): gdy nastąpi zmiana (np. telefon leżący na półce nie będzie raportował gyro nawet przez wiele godzin / całą noc.