Fix IBB

Closes #8196

See merge request !90

- Move handling of Data IQs into IBBIqHandler
- Call SendHandler with file_props
- Save last sent id in file_props.syn_id
- Remove some useless checks, now that we call SendHandler with file_props
- Send item-not-found error on invalid session id

Logs.db is always at data_root, even if we set another config directory with -c

fix "Unable to load icon gajim" errors caused by !84

See merge request !87

use 'reverse DNS' convention for desktop and icon files

See merge request !84

HistoryManager was not finding the Logs.db when Gajim was
used with the -c config path argument

fix python errors in client zeroconf

See merge request !82

Disable button if password changing is not supported

See merge request !85

see https://specifications.freedesktop.org/desktop-entry-spec/latest/ar01s02.html

Implement chatstate in MUC, as defined in XEP-0085 §5.5

See merge request !11

python-gnupg uses latin1 as default encoding because GPG itself uses
latin1 as default.
We should not override this default with getpreferredencoding, because
getpreferredencoding maybe returns something else than what GPG is configured
on that system.

Example: On Windows
GPG is run in default mode with 'latin1'
getpreferredencoding returns 'cp1252'

The approach would be now to default to latin1 as it is GPGs default.
And if the User sets a different ecoding for GPG he has to set it in
Gajim aswell.

- Handle exceptions inside write() instead of propagating the
    exception
- Add error message to exception
- Add dispatch() method in logger

- Pass EventObj instead of variables
- decrease indent level
- check all conditions inside log_message() not before calling
- fixed bug where gc private messages where not logged with the correct jid

use a class method to remove the resource from JID

use ascii_letters which should be sufficient

Sending Message Refactoring

See merge request !80