Implemented proper fragment support

   1. Moved background tasks (Eiscp, etc) to a background/headless Fragment
   2. Implemented first-pass Interface-based callback mechanism (needs
      cleanup/restructuring, but it works for now)

Other misc. cleanup:

   1. Removed status flags from Eiscp (ReceiverInfo now tracks this info).
   2. Removed unneeded packet parsing, replaced with optimized processing.
   3. Optimized initializeConnection to start one thread that queries all
      status, rather than one thread per query.
   4. Do not send Source selection command to server if the source is the
      same as currently configured.