Add SelectionOptions type and refactor GetThermostat to use them

[cvvs]

I wanted to be able to configure GetThemostat selection data, and you have a TODO to allow for this, so I created a SelectionOption type which can be passed into GetThermostat to set specific selection options when making a request.

I modified the GetThermostat to take the options as a variadic parameter, so the change should be backwards compatible.

Originally, the option funcs were all With<SettingName> but that seemed redundant, so removed the With.

I can undo the formatting changes made by gofmt if you prefer.