Proposed tSen Flag For Improved Signalling of Control Period
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DHD20160830

https://opentrv.atlassian.net/browse/TODO-972

Detecting when the energy saving features have been disabled with tS|C is proving messier than hoped.

When such features are temporarily disabled for a control with the G 0 parameter please also include an extra JSON parameter in the output, and remove it otherwise, something like "tSen":"0". It can be marked as a low-priority value, ie only need be sent occasionally to save bandwidth.

The same function should be used to drive both to avoid them getting separated over time.