snet: Add stringer to path (#3290)
snet: Add stringer to path (#3290)

This allows to retreive human-readable path representation for
logging and debugging purposes.
Oncilla/scion,Oncilla/scion,netsec-ethz/scion,netsec-ethz/scion,Oncilla/scion,Oncilla/scion,netsec-ethz/scion,netsec-ethz/scion