Dialogs: Use get_widget_for_response() to access buttons

See merge request gajim/gajim!178

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.

Fixes #8806

When a ping reply is received there is probably a connection. Anyway, the
last ping might have been lost and the ids might not match up.

The new Placeholder text inside MessageTextView was causing many
buffer changed events.

- Add a method that lets us know if there is user input
- Add logging

Fix xmpp: URI handling.

See merge request gajim/gajim!170

Remove gajim-remote.desktop and fix gajim.desktop

See merge request gajim/gajim!169

It was previously removing the first three characters of the JID, and
ignored any URI without an action.