First release

Fully working release.

What it can do:
All basic settings can be controlled, i.e. mode, power state, fan speed, horizontal vanes (including swing), and temperature set point. Ambient temperature is reported but needs to be calibrated more accurately.
Settings (WiFi network and MQTT) will be stored in flash memory.
The ESP-01 will always try to reconnect to the network after it has been down. If it fails, the configuration portal is started. If it is not accessed within a user definable time period, it will try to reconnect to the router using the existing settings. It is therefore safe to install this system in hard-to-reach places.

What it can't do:
The vertical vanes cannot be controlled via serial, just the horizontal vanes.
Auto fan speed and (3D) auto vanes cannot be controlled via serial.
High power and economy modes can also not be set via serial. These appear to be presets of available settings (?).
Error codes, filter cleaning etc. is supposed to be reported over serial also, but it is really hard to find out what the codes are.