Added OLED functionality

[luckypants123]

Lots of changes - I've tested it and believe all the bugs are worked out.

• Obviously OLED support.
• MQTT topic structure is a bit different (detailed in readme and in sketch).
  • State topic format is {"state":"idle","id":0}. ESP publishes states idle, reading, matched, not matched, learning, deleting here, as well as the appropriate id.
  • Request topic format is {"request":"learn","id":"6"}. ESP is subscribed and watches for requests learn, delete, as well as corresponding id. The JSON is deserialized and the learn and id are separated at the top of the function.
  • Reply topic format is {"line1":"HELLO IAN","line2":"SYSTEM ARMED"}. ESP is subscribed and displays line1 and line 2 on the OLED. This is intended to be triggered in an automation... its something of a confirmation that the automation you've mapped to that print id has fired.

Included are the relevant yaml files.

I didn't re-implement the Home Assistant MQTT sensors for reading, learning, deleting as the information is displayed on the OLED - you may want to add these if desired.

[EverythingSmartHome]

Looks great, thanks!