Add support for XEP-0368

See merge request gajim/gajim!177

Fixes #8801

On destroy() the window that was last focused gets the focus
again. if destroy() is called from the StartChat Dialog, the new
ChatControl is not yet focused, because present() seems to be asynchron,
at least on KDE, and takes time.

set_active_tab() already calls present(), no need to call it afterwards
again

Refactor some Tooltips

See merge request gajim/gajim!180

Add ad-hoc commands for Groupchats

Closes #8819

See merge request gajim/gajim!179

- Dont create a Tooltip window
- Just return the tooltip grid, so we can use it with set_custom()

We dont needed anymore

Fixes #8819

Dialogs: Use get_widget_for_response() to access buttons

See merge request gajim/gajim!178

 - Use xmpps-client SRV records
 - Use separate host entry per connection type
 - Replace 'connection_types' with 'allow_plaintext_connection' option

The get_action_area() API is deprecated and under some circumstances
the wrong button gets accessed.

Fixes #8810

Also remove mam_start_date migration.
mam_start_date didnt exist in Gajim 0.16.x and it doesnt hurt
if people who used the dev version download some extra messages.
Our deduplication algorithm should take care of it.

GUI interface: fix resource warning

See merge request gajim/gajim!175

Zeroconf: fix unexpected keyword argument

See merge request gajim/gajim!174

_update_status() got an unexpected keyword argument 'idle_time'

introduced by 28917aaf

Zeroconf: Fix get_own_jid()

See merge request gajim/gajim!173

height() and weidth() is not supported any more

Action Button was removed in the last ChatControl redesign

Remove incorrect assert

See merge request gajim/gajim!171

We need it later as JID object

This field was added but never used

This does not remove the columns from the DB, but doesnt add them
in new migrations.