Its for the Whiteboard Plugin

- Set application and menubar
- Remove deprecated settings

Fixes #8756

- Sort imports correctly (PEP8)

Avatar Refactoring

Closes #8743

See merge request !135

- Add support for Pubsub Avatars
- Dont poll for vCard Updates, only use XEP-0153
- Dont cache vCards
- Store the avatar SHA of roster contacts in the DB
- Store the current SHA of each contact in the Contacts Object
- Move some code into the ConnectionVcard Class

Update setup.py and .gitignore

See merge request !142

Fix deprecation warnings

See merge request !143

add flatpak support

See merge request !83

Replace make_color_string() by Gdk.RGBA method

See merge request !141

AppData: update information

See merge request !139

tim is epoch, time.localtime() a struct_time

Fixes #8752

Fixes #8753

Simplify check_X509.py

See merge request !140

as pyasn1 and pyOpenSSL are required now

Update README

See merge request !138