Rework networker

Rework networker

  - keep netconfigs in hash; create the usual deserialize/delete/... functions
  - keep the netmap in hash; create the usual de/serialize/delete/... functions
  - change sequence: serialize & save netmap; combine spoolfiles; free netmap.
  - use strbufs splice() wrappers to combine the message-spoolfiles into host-spoolfiles instead of forking a shell & running cat + rm
  - when appending to host-spoolfile fails, remove partial adds to avoid creating invalid spool control files
  - only cleanup spool directory if we successfully combined all files; else we might loose messages if i.e. a networker is running for that node.