Split out experimental "stream" protocols; make tcp.rkt use them; more inertness checks

Also, a few other important changes:
 - Better printing of entity-ref structs
 - Inertness checks on assertion retraction (!) and preventer-disarm
 - Correct selection of active facet during dataflow recomputations
 - Repair silly omission in turn-assert/dataflow!

stream.prs

@@ -0,0 +1,43 @@
+version 1 .
+embeddedType EntityRef.Ref .
+
+StreamConnection = <stream-connection @source #!Source @sink #!Sink @spec any>.
+
+; Assertion
+StreamListener = <stream-listener @spec any @handle #!ConnectionHandler>.
+
+; Assertion
+StreamConnect = <stream-connect @spec any @handle #!ConnectionHandler>.
+
+; Assertion
+ConnectionHandler =
+  / @connected <stream-connected @source #!Source @sink #!Sink>
+  / @rejected <stream-rejected @message string>
+.
+
+; Assertion
+StreamError = <error @message string>.
+
+Source =
+  ; Assertions:
+  / <sink @controller #!Sink>
+  / StreamError
+
+  ; Messages:
+  / <credit @amount CreditAmount @mode Mode>
+.
+
+Sink =
+  ; Assertions:
+  / <source @controller #!Source>
+  / StreamError
+
+  ; Messages:
+  / <data @payload any @mode Mode>
+  / <eof>
+.
+
+CreditAmount = @count int / @unbounded =unbounded .
+
+Mode = =bytes / @lines LineMode / <packet @size int> / <object @description any>.
+LineMode = =lf / =crlf .

tcp.prs

@@ -1,25 +1,7 @@
 version 1 .
 embeddedType EntityRef.Ref .
 
-Connection = <connection @handle #!ActiveSocket @spec any>.
-ConnectionPeer = <connection-peer @handle #!ActiveSocket @spec any>.
+TcpRemote = <tcp-remote @host string @port int>.
+TcpLocal = <tcp-local @host string @port int>.
 
-TcpRemote = <remote @host string @port int>.
-TcpLocal = <local @host string @port int>.
-
-ActiveSocket =
-  / <controller @controller #!Sink>
-  / <close @message string>
-  / Socket
-.
-
-Socket =
-  / <credit @amount CreditAmount @mode Mode>
-  / <data @payload bytes @mode Mode>
-  / <eof>
-.
-
-CreditAmount = @count int / @unbounded =unbounded .
-
-Mode = =bytes / @lines LineMode / <packet @size int>.
-LineMode = =lf / =crlf .
+TcpPeerInfo = <tcp-peer @handle #!any @local TcpLocal @remote TcpRemote>.