Add an option to scan if there is a partial file already downloaded and pick up where it ended

[CodeCubeNeo]

Or does that have to be a change to the warpinator logic? It would be very good for bigger files to continue sending data, where it left of.

[slowscript]

This would require changes to the protocol, so the receiver could tell the sender where to start. Maybe bring this up with the original authors at linuxmint/warpinator?