handle XEP-191 (blocking command) in a better way: hability to block a contact when server doesn't support privacy lists, add / remove jid to blocked list only when we get the result from server, handle blocked / unblocked contacts by other resources

This will make Gajim start a bit faster and more entropy can be
generated for key generation.

Fixes #7735.

After the random number generator seed file is read overwrite the
previous content of the file.

Jingle File Transfers work without Farstream.

ICE-UDP transport is also implemented as a part of Farstream (libnice)

Fixes #7713

Avoid DepreciationWarning for ImageMenuItem, CheckMenuItemi, and MenuItem.

Fix #7858

Signed-off-by: Matěj Cepl <mcepl@redhat.com>
---
 src/chat_control.py          |  8 +++----
 src/conversation_textview.py |  5 ++--
 src/groupchat_control.py     |  4 ++--
 src/gui_interface.py         |  2 +-
 src/gui_menu_builder.py      | 15 +++++++-----
 src/roster_window.py         | 56 +++++++++++++++++++++++++++-----------------
 src/statusicon.py            | 13 ++++++----
 7 files changed, 61 insertions(+), 42 deletions(-)

There are many warnings

    Using positional arguments with the GObject constructor has been
    deprecated.

cluttering stderr needlessly.
Fixes #7855

Fixes #7664

Signed-off-by: Matěj Cepl <mcepl@redhat.com>