Dynamic heartrate

[ebaauw]

As suggested by @dylanslewis (in issue #4), allow for changing the polling interval from HomeKit instead of from config.json. Add a StatefulProgrammableSwitch service to the Homekit accessory for each bridge, mapping the heartrate to Output State and the time of the last sync to Last Updated. Could even use Switch and use On to turn off polling altogether.

Notes to self:

• Need to change setInterval() loop in HuePlatform.accessories() to fire every second and call HueBridge.heartbeat() with counter and check for counter % heartrate === 0 in each bridge.
• Need to change the handling of "get" events from HomeKit to issue ad hoc bridge state refresh when heartbeat is off.

[ebaauw]

Dynamic heartrate implemented in v0.1.8.

Disbabling heartrate not yet implemented, as handling of "get" events is more elaborate.

[dylanslewis]

Amazing, thank you!