Add Support for new Set Temperature commands

Using the latest nefit commands, add the ability to use more specifiers to the the temperature relative to current setpoint or current temperature.
Also makes it possible to specify a constant value to pass to Set Commands, simplifying flows.

Add User Mode Support

Makes it possible to get and set the User Mode of the Nefit to "Manual" or "Clock"

Latest Nefit Integration and Add Fireplace Mode Support

Merge pull request #3 from RaimondB/add-help-text

Add help text