UAVO browser was emitting updates on every UAVO receive event. This was
inefficient and led to a high processor usage, as well as causing the
browser to drop a high percantage of updates.

The patch centralizes the dataChanged emits, and places them on a timer.
UAVO browser processor load fell over 50% and data updates beyond 3Hz are
now reliably shown.
Updated updateChanged() throttling to act directly on view, instead of data.
Moved all awareness of update ranges out of data model and into tree view.
Added dynamic throttling to UAVO browser. The throttling updates the UAVO
browser at the speed of the fastest visible UAVO, up to a certain
threshold. After this threshold, the throttle is scaled exponentially,
such that the maximum refresh rate is around 30Hz.
Merge pull request #316 from kubark42/uavobrowser_update_fix

Fix for UAVO browser emit flooding