revision of SECoP documentation

- created secop_v2017-09-14.rst, based on the GoogleDocs
  SECoP Preliminary V2016-11-30 (rc 2)
- this Document is supposed to contain the full SECoP standard
- created SECoP issues
- moved everything else to "outdated" (kept for reference)

Change-Id: I87d69d1846fc4ed55f1c78b22fd4650d8550152b
Reviewed-on: https://forge.frm2.tum.de/review/16573
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>

doc/source/protocol/issue_6.rst

@@ -0,0 +1,23 @@
+SECoP Issue 6: Keep Alive (under discussion)
+============================================
+
+For a SECoP server, in order to detect that a client connection is dead,
+it might close a connection with no messages within a defined period of time.
+
+The discussed mechanism is:
+
+The SECoP client has to set the connection parameter 'keepalive' to a value
+representing the number of seconds it will send 'ping' (or other) messages.
+The SECoP server can close connections with no messages for a time period
+well above this value (more than 10% higher).
+
+Opinions
+--------
+
+Markus proposes to mention the 10 % in the specification.
+It should also be mentioned, that for keeping the connection alive
+any message might be sent instead of the ping message.
+
+
+Decision
+--------