Route multiplexing / multipath

[0pcom]

Currently, applications can make use of only one route to a remote. Skywire apps such as the VPN would benefit from a route multiplexing module that allows to open and use multiple routes. This would not only help in instances of congestion on a route or if a route drops ; in theory this could be implemented such that traffic transits multiple multi-hop routes between two machines. This would be very similar to bittorrent - and should facilitate greater bandwidth between two machines than is normally possible via a direct connection or a route consisting of a single direct transport between two machines.

Old ticket: https://github.com/skycoin/skywire/issues/440