Small code quality tweaks

What's Fixed

• Update requirements (e.g. paho-mqtt is no longer <= 2.0.0, #168)
• Throw a warning if it appears that the RAMSES_ESP dongle hasn't has its SNTP settings configured
• For 3EF0, hex_to_percent() now is high-resolution

Full Changelog: 0.50.0...0.50.1

Release 0.50.0

First release:

• dependency upgrades
• bugfixes
• performance improvements
• removing code smell (e.g. I/O in `init.py``)
• less logspam
• better testing, less lint
• parser tweaks, esp. HVAC (thanks @silverailscolo)

Is targeted at Python 0.13, but should be OK with 3.11.