Custom Data Processing.md. More info needed.

[bryn51]

There is a paragraph that reads:
Data is processed in a recurrent manner whenever there is postprocessing in the device. You can check it by visiting https://api.smartcitizen.me/v0/devices/ where is the number that follows in the url https://smartcitizen.me/kits/XXXXXX

This document should provide a little more info on how to find the missing XXXXX and
I found that when you visit https://smartcitizen.me; open your profile, the URL found under "view on Map" button (hover over it with the mouse) provides this information. easy to add this guidance; and necessary as there is no-where else it can be found.