Add an asynchronous HTTP server

[tcalmant]

I'm working on a branch (http_async) to add an implementation of the HTTP service based on aiohttp.

The objectives is to provide the following features

• Maintain compatibility with the synchronous API
• Ensure that the synchronous servlets behave similarly as with pelix.http.basic
• Ensure that the routing utility works the same
• Add support for an asynchronous request/response mode
• Add support for long queries (Server-Sent Events)
  • Add tests
• Add support for WebSocket "servlets"
  • Add tests
• Add tests for basic async handler feature (same as sync)
• Add documentation

This feature is required for future projects.

[tcalmant]

Added initial support for websocket, tests to be added

[tcalmant]

Added initial support for SSE

[tcalmant]

Tests added, ran on Python 3.12 on Windows.
Added initial version of a documentation (to be enhanced with API descriptions and snippets to be tested)