Fixes #8663

https://tools.ietf.org/html/rfc7622#section-3.2

Update JingleFT support, and fix sending files

See merge request !89

'channel-insecure-symbolic' icon if no encryption is selected

'channel-secure-symbolic' if an encryption is selected

Fixes #8652

Update servers.xml

See merge request !101

This crashes Gajim on Windows.
Its to be investigated why this happens and how we can avoid it.

Fixes #8649

self.encoding which we set in the init is only intended
to decode gpg´s stderr which uses a system specific encoding.

if we dont encode the data we pass to python-gnupg ourself, it will fallback and use self.encoding.
This might be of no concern if self.encoding is set to 'utf8' and when we are on Linux
which has a preferred encoding of 'utf8'.

But if we are on Windows the preferred encoding for stderr
is most of the time not 'utf8'. If python-gnupg tries to decode a stderr stream that is for example
encoded with 'cp1252' with our set encoding of 'utf8' this will fail.

The solution is to pre-encode the data before we pass it to python-gnupg, so it does not have to
use self.encoding as a fallback. And set self.encoding='latin1' because latin1 will not yield exceptions
on decoding errors. Also gpg itself will fallback to latin1 as stderr encoding when it cant determine the
preferred encoding of a system.

self.decode_errors is used for something differently, and has no influence on the situation.

Fixes #8644

There are mutliple reasons why this is not a good idea

1. It places work on encryption Plugins, as many encryption attributes inside the
stanza can not be resend again (OMEMO, OTR), so the plugins have to make sure none of
these attr are inside the LMC stanza

2. In general its not obvious for plugin devs that a stanza issued after LMC has to be
treated differently. There should be no negative effects, even when a contributor not knowing
about LMC at all.

This commit saves only the stanza id, and adds the replace tag on the new message.
This results also in less code.

There is no reason that any Groupchat should be treated as already connected when we sign in.

Some of the Commands have security implications, thats why we disable them per default
Fixes #8378