slixmpp 1.5.0 release

- Add ids to presences and messages by default
- Fix various issues in connection/disconnection
- Code improvements (typing, deprecation warnings)
- Fix or improvements for the following XEPS:
    - XEP-0045
    - XEP-0048
    - XEP-0050
    - XEP-0059
    - XEP-0082
    - XEP-0196
    - XEP-0198
    - XEP-0202
    - XEP-0279
    - XEP-0332
    - XEP-0313
    - XEP-0323
    - XEP-335
    - XEP-0380
- New XEPs:
    - XEP-0359 (origin-id)
    - Groundwork for the OMEMO (XEP-0384) plugin, which has been put in
      a separate repository due to licensing issues:

Many thanks to all first-time and recurring contributors!

Special thanks to pep. for being the most active of the maintainers
and for the OMEMO work, to Madhur Garg (GSoC student) for fixing the
MAM and RSM implementation, and to Georg for trying to fix the
connection shenanigans.