Add template support to climate.mqtt

The climate.mqtt really needs templating for all of the command and state topics it uses. For example, my thermostat uses “0” and “1” as the fan modes and hold modes and “O”, “H”, “C”, “A” as the system modes. I need to be able to translate these into modes into something which HA can understand.

While we’re at it send_if_off is supposedly defaulted to true which should basically ignore the power_command_topic (which my system does not have) but this doesn’t seem to work as making adjustments in HA does not seem to fire off any MQTT messages.

Thanks!

Related: Templating is needed for the target temperature as well. By default this seems to send temperatures with decimal points (eg. 70.0) to this topic but my thermostat only supports integers. This could be handled with a template as well.