SenderReceiver: add a print_debug() method to more cleanly print debug info
SenderReceiver: add a print_debug() method to more cleanly print debug info

Obviously printing out the entirety of a signature or a delta
in the debugging is basically useless.  It could be multiple MB
in size, and just makes trying to find stuff at all.  Obviously,
this resolves that

arbenina/syncdiff,warthog9/syncdiff,arbenina/syncdiff,warthog9/syncdiff,warthog9/syncdiff,arbenina/syncdiff