Addition of developer and user modes to debugcli

In order to be able to protect the interface so that mistyped argument
do not endanger MaxScale yet still allow the developer access a router
option has been added that gives the debugcli two modes.

server/core/session.c

@@ -269,6 +269,34 @@ return_succp :
         return succp;
 }
 
+/**
+ * Check to see if a session is valid, i.e. in the list of all sessions
+ *
+ * @param session	Session to check
+ * @return		1 if the session is valid otherwise 0
+ */
+int
+session_isvalid(SESSION *session)
+{
+SESSION		*ptr;
+int		rval = 0;
+
+	spinlock_acquire(&session_spin);
+	ptr = allSessions;
+	while (ptr)
+	{
+		if (ptr == session)
+		{
+			rval = 1;
+			break;
+		}
+		ptr = ptr->next;
+	}
+	spinlock_release(&session_spin);
+
+	return rval;
+}
+
 /**
  * Print details of an individual session
  *