Add support for HTTP 2.0

[VigneshVSV]

Support version 2.0 of HTTP

Steps involved:

• Check tornado's HTTP 2.0 implementation, I made a fork which fixes a bug (https://github.com/VigneshVSV/tornado_http2), merge it back to tornado and get their latest commits
• If tornado is not stable, find another async provider?
• Implement Property, Action and Event Handlers and all other handlers necessary/ carry over existing handlers if possible
• Setup middleware to handle authentication
• Add option to user to choose the HTTP server and its version. Add same option to the to run_with_http_server method of Thing class
• Test. If possible, get some numbers regarding the performance in a comparative manner

Either package it with our release or add to pip dependency in pyproject.toml

Before working on the complete implemetation, we should probably agree on which HTTP 2 provider will be used.