Cleanup of shutdown of event contexts

  - centraly mark citcontexts connected to AsyncIO structs for deletion
  - free AsyncIO members in FreeAsyncIOContents() and make shure its called all over the place
  - sort stopping of contexts by type
  - close our DB/event - add pipes on exit
  - reshuffle RSS Aggregator; all parsing etc. to rss_atom_parser.c, all free/start/stop to serv_rssclient.c
  - remove unused stuff now discarded from the rss header
  - rename all instances of the rss aggregator struct to RSSAggr