DHT fix
Merge pull request #932 from egbertbouman/fixes

DHT fix
Cleanup exit sockets immediately on create timeout
Use get_session to get the libtorrent session
Merge pull request #937 from egbertbouman/fixes

Fixes
Fix
debugs
disable metadata community
add TFTP service
change RemoteTorrentHandler to use TFTP
change code that uses download_torrent() of RemoteTorrentHandler
change Session download_torrentfile() and download_torrentfile_from_peer() and code that uses them
create RemoteTorrentHandler unit test
remove SwiftEndpoint
simplify TFTP and make TFTP queue
disable fallback magnet download
RemoteTorrentHandler cleanup
create tarball for directories using TFTP
change metadata to use TFTP
add metadata download test