Supported "Heat To" / "Heating To" and several other bug fixes

[zimuliu]

This PR contains multiple changes on the forked repo

• Supported "Heat To" / "Heating To" (the issue reported in https://github.com/dustindclark/homebridge-rinnai-controlr/issues/2)
  • Always set Heat as target state (will show "Heat to" in Home.app)
  • Set Heat as current state when combustion is on (will show "Heating to" in Home.app and the number will turn Orange); otherwise, set Off as current state (the number will stay White)
  • Display the outlet temperature as the current temperature, so that it better match the UX of ("Heat to" / "Heating to"). Note that we pull the outlet temperature at different frequencies, so that we don't congest the API for setting a new target temperature.
• Fixed the incorrect use of _.throttle
• Avoided to create RinnaiControlrPlatformAccessory for each poll
• Fixed the HomeKit Accessory UUID generation
• remove unused device
• Use dynamic step sizes for controllers with imperial units
  • The controllers in US/Canada use step of 2, like 98F/100F/102F/etc. for the temperature below 110F. We need to use the right step number during the rounding, so that we can avoid the rounding error.
• Changed the default max/min from the manual (98/120)

Example when the combustion is on

Example when the combustion is off