Deduplicate based on stanza-id

See merge request gajim/gajim!148

- Add methods to determine the unique/stable id
- Write the id to the stanza_id DB field
- Add method to deduplicate based on the unique/stable id

- Calculating so many hashes for each Message is quite expensive
- It hides our own implementation bugs, like when we retrieve history
from a MUC with wrong timestamps, or on rejoin. We never know about it
because the Messages are dropped.
- It should not be necessary anymore. The original problem was a bug
in nbxmpp which triggered mass resending of old messages.

- Show new Symbol if a feature is available but not enabled
- Add this info to the tooltip

- add get_oob_data() so we can use it on more than one event
- also remove a forgotten print call

Add extension points to history window

See merge request gajim/gajim!147

Right now oob data is merged into the message text and stored into the DB.
If we load this message from the DB we cannot know anymore if and which
parts of the text was oob data.

Use the additional_data api to store oob data into the DB instead of
altering the original message text.

This lets us decide later on if and which data we want to display, even
on history replays. Also plugins can use the data.

Fix additional_data in events

See merge request gajim/gajim!146

Plugins or other code can pass custom Options

Fixes #8773

This also adds that Gajim gets present if Gajim is launched a second time

Its enough to connect to the handle-local-options signal for what we
currently want to do.

If the JID is not in the DB we need a type to insert

New Style for Chat Windows

See merge request gajim/gajim!144

- Move ActionBar into HeaderMenu
- Make Design of ChatControl look cleaner
- Hide the Roster in Groupchats per default
- Add Button to hide/show Roster in Groupchats
- Move Groupchat topic into popover
- Display Avatars on the right side of the ChatControl and status on the
left
- Add a default Avatar for contacts that have none

the account name was passed instead of the account jid

- make it use get_jid_id() and return the jid_id

Use _jid_ids dict instead