Allow specifying the controller "identifier" on the command line

[SphtKr]

The current default value is aqualogic. Depends on #1. Mainly this will allow adjustment of the MQTT topic path and some of the metadata values that are ultimately used to build the HA entity_id.

Technically...this would allow multiple pool controllers to be recorded in a single MQTT broker which is not possible otherwise... maybe there is some testing use case for this.

Easy but fairly low priority unless I get requests.