now that file params has more work to do we should make sure we always call it from a sperate thread

Conversations and Gajim both have an implementation bug that sends the jingle session id instead of the transport id (compare XEP-260 2.2). This commit has a work around for this that remains buggy when using ft:3. If gajim is ever to fix this we will be incompatbile. gajim should implement ft:4 instead. (gajim to gajim is broken as well)

Update create_conference_dialog.xml to also match dark theme.

Updated to the text color attribute so it fits to the bright and dark theme appropriately.