Fixes #10055

Fixes #10051

gajim.desktop isn't provided since 1.0.0.
The change might fix detection of Gajim nightly in GNOME software.

Fixes #10049

Icons are generated from Source using App Icon Preview

When we are connected to the server we need to set some things up
before we send our initial available presence. The new state makes
it possible for other code to difference between when we are connected
and when we are available.

For example other code should not send a presence before we requested
the roster.

Fixes #9983

- Let nbxmpp handle responding to entity caps requests
- Move code into Caps module

Fixes #10044

Otherwise its not really portable if it stores data in the system keyring