AIDA: make Lib::ProtoSignal use protected
RCORE: use C++11 'delete' keyword for methods of non-copyable classes
AIDA: include C++11 <future> for promise & future types in async signals
AIDA: add AsyncSignal for asynchronous emissions based on std::future
AIDA: allow std::move for AsyncSignal handler arguments by using std::forward
AIDA: Signal: factor out HandlerLink (SignalLink) to allow reuse
AIDA: Signal: emit: keep references to all links of captured handler list
AIDA: remove experimental signal collector support from IDL
UI: window: prepare to handle sig_commands as asynchronous signal
AIDA: CxxStub: generate non-void return value signals as AsyncSignal
AIDA: CxxStub: whitespace fixup
AIDA: better fit for MessageId, add ids for async signals
AIDA: assertion simplification
AIDA: some symbol renames for clarity
AIDA: rename NullSmartHandle.__aida_typelist__()
AIDA: xmanifold.py: handle stray comma
AIDA: implement asynchronous signal emission processing

* AIDA: prepare emit_result_handler on ServerConnection for async signals
* AIDA: connect asynchronous signals via connect_future()
* AIDA: ClientConnection: dispatch MSGID_EMIT_TWOWAY
* AIDA: allow renew_into_result() directly from FieldBuffer
* AIDA: send back EMIT_RESULT from client signal handlers
* AIDA: ServerConnection: dispatch MSGID_EMIT_RESULT
UI: process sig_commands emission fully asynchronously from Window event loop
AIDA: Python: return emission results or raise descriptive return value exception
AIDA: Python: cleanly handle exceptions from signal handlers