BUGS:
AdressElements != MSymbols (e.g. may contain @'s)
HOSTLOCAL: setsockopt IP_TTL=0 is not supported by module socket

TODO:
Config: Address=BROADCAST
check for config version
probably recalculating of hello_d could be optimized
honor mbus.waiting and mbus.go
need to fine tune scheduler timeouts?
implement anycast rpcs

Ideas:
* Callbacks on messages matching a given address?

Perfomance:
* Check hmacs only if msg is addressed to us
* use perfomance tips from http://manatee.mojam.com/~skip/python/fastpython.html
* add constants mbustypes.type_int = type( 123 ), mbustypes.type_float = type( 3.14 ) ...


Incompatible Changes:

v0.2 -> v0.3

mbusguides.py:
    * Serverside RPCs now have to return a RPCReturn object or may throw an
      RPCException
    * sendRPC callbacks now only have ONE argument. This argument is a list of
      triples. In case of a multicast rpc the list may contain more then one
      element. Each triple consists of ( Address, Status, Result ). 
