Use precis instead of stringprep when available. Fixes #8566

See merge request !116

Our loader cant load compiled sourcefiles

Not all Dialogs have a window instance, some inherit Gtk.Window

Redesign XML Console

See merge request !115

- Use modern GTK Widgets (HeaderBar, ActionBar, Switch)
- Add an option to filter Stream Management stanzas
- Add a generic Option Dialog that we can reuse later

run tests in gitlab-ci on every commits

See merge request !114

- Execute as script to save roundtrips

- Dont depend on get_jid_id(), this saves roundtrips

- This is added because even an ignored INSERT raises the
autoincrement value of the table.
This means the jid id gets high really fast.

- It should be where all other message received handlers are
- Port to new DB API

As we always load plugins from the user path first, we should not
reload them later from Gajims plugin base dir

Remove plugin path from sys.path after importing.

If we scan multiple plugin dirs and never remove the path from
sys.path, it is hard to predict from which path python will import
a package.

The chance that the same plugin package is in multiple plugin paths
is high.

This is a MUST see https://xmpp.org/extensions/xep-0234.html

Fixes #8662

- XEP-0234 demands UTC
- we missed the 'Z' at the end
- simplified the code

Simplify whats left

- also save stanza id to the DB