Add XEP 0060 and 0363

[selfhoster1312]

This PR adds support for file uploads/downloads by adding upload Slot to the Recv function as well as typed Oob entity so that OOB URLs are parsed on incoming messages too.

I also added a few tests.

I made this PR because i was doing something like this on matterbridge but it was cumbersome, and i thought it would benefit other people as well.

Not implemented here:

• auto-discovery of the file upload component / max upload size
• querying a file upload slot
• uploading the file via HTTP

[mdosch]

I will need some time to review this. Maybe during the christmas holidays.

[mdosch]

Thank you very much, I found some time yesterday and it works well but I am a bit reluctant about the change with the Oob type as this will break implementations using Ooburl and Oobdesc.
We have a 0 version, so there is no promise of stability but we should break things unnecessarily.
Maybe we should support both for a while and print a deprecation warning when using the old style to give implementations time to adapt without breaking?

[mdosch]

Done