Lots of new features added to this driver

[tgnorman]

I have implemented and tested many of the more advanced features provided by this device. Probably need someone at Core to review, I am happy to write up some documentation about best practise that I have found in using these new methods.

The main additions are:

1. get/setMeasurementTimingBudget (this made a HUGE improvement in mesurement consistency - see below)
2. get/setDistanceMode - short/medium/long
3. get/setROISize - select from 16x16 down to 4x4 sensing elements (SPADS), thereby narrowing the field of view/region of interest
4. get/setROICenter - change point of focus
5. singleMode - set read mode to "single"
6. readSingle - read one value and stop - instead of continuous "ranging" mode
7. start/stopRanging

These methods require some helper functions, which are included, but would NOT normally be considered part of the user API. For internal consumption only!

In my bench tests (and in the wild) I found increasing the timing budget from the default (about 95 miliseconds) to 200, or 300 ms, provided dramatic reduction in the standard deviation of measurements, across all three distance modes. Sometimes even 400ms worked well, but the improvement over and above say 300ms is not great... at the expense of slowing down the rate of measurements returned.

Hope you like it! It has transformed a kinda inaccurate device into one that in most cases consistently measures to within a millimeter or 2...
Regards, T.