Jingle File Transfer and XTLS support for gajim

by Zhenchao Li(fantasticsid) for XMPP Standards Foundation

Jingle is an advanced protocol for negotiating and managing media sessions between two entities. File transfer over jingle is currently not supported in gajim. I propose to implement jingle file transfer for gajim and add support to XTLS for data encryption. This will both benefit users of gajim and serve as another implementation of jingle file transfer and thus help the XSF community to better shape related protocols.