Simplifying the IOT framework's API

This post is more of a changelog combined with an explanation of my thought process for the changes.

c50b112 - Use the publish function only from common instead of directly from mqtt. Doing this removes the requirement from the client to verify if the mqtt object has been initialized.

d6df15c, 8a3d443 - Add logging on OTA updates & log using explicit indexes on OTA updates, this allows extra fields to be sent (and ignored).

f576c69 - Require subscription topics to be provided as a list, this simplifies client setup. Move OTA logic out of mqtt client creation

f2b03bb, 219e560 - Ignore and remove _id argument in loop – we can now obtain that from a file called HOSTNAME (or fall back to the device's MAC address).

5a59852, fba9be8 - Make rebooting optional while doing OTA. This allows you to push changes across multiple files, that otherwise would be backwards incompatible.

1a93289, a9a6911 - Restructure layout for easier multi-file update

$ tree firmware
firmware/
├── common.py
├── curtains
│   ├── common.py -> ../common.py
│   ├── HOSTNAME
│   ├── main.py
│   └── mqtt.py -> ../mqtt.py
├── mqtt.py
└── rfsocket.py

With this setup, you can cd into a device's directory and run
mpfshell ttyUSB0 -c 'put common.py; put main.py; put mqtt.py; put HOSTNAME; repl'
to bootstrap a new device.
Subsequent updates can be done OTA.

fdf76d9 - Set hostname in AP config – this change makes it more clear which device is which on network inspection, there's no longer a list of ESP-8D... devices.