specifically, all of the performance platform specific data layout now
happens in performance_platform_client.py - stuff like setting the
_timestamp, period etc, and the perf platform-specific nomenclature is
all handled there.
so that it doesn't appear generic when it's actually specific to
sending the daily notification totals. To do this, split it out into a
separate performance_platform directory, containing the business logic,
and make the performance_platform_client incredibly thin - all it
handles is adding ids to payloads, and sending stats.
Also, some changes to the config (not all done yet) since there is one
token per endpoint, not one for the whole platform as we'd previously
coded
