fixed missing initialization

in constructor
extended broker and added simple(r) broker example

this patch adds the member functions `add_connection`,
`add_tcp_connection`, `add_acceptor`, and `add_tcp_acceptor`
to the broker class and adds the simple_broker example to
showcase the broker API without Google Protobuf overhead
updated documentation, updated ChangeLog
Merge branch 'master' into unstable
moved tuple_dummy to its own header