implement global keep alive option

keepaliveInterval in config.json. time in ms, 0=disable

app.js

@@ -54,7 +54,8 @@ app.get('/ssh/host/:host?', function (req, res, next) {
     },
     readyTimeout: (validator.isInt(req.query.readyTimeout + '', {min: 1, max: 300000}) &&
       req.query.readyTimeout) || config.ssh.readyTimeout,
-    verify: config.verify || false
+    verify: config.verify || false,
+    keepaliveInterval: config.keepaliveInterval || 0
   }
   if (req.session.ssh.header.name) validator.escape(req.session.ssh.header.name)
   if (req.session.ssh.header.background) validator.escape(req.session.ssh.header.background)

config.json

@@ -59,5 +59,6 @@
     "server": false  // not yet implemented
   },
   "accesslog": false, // http style access logging to console.log
-  "verify": false // verification of host key hashes, see hostkeyhashes.json
+  "verify": false, // verification of host key hashes, see hostkeyhashes.json
+  "keepaliveInterval": 0 // value in milliseconds, 0 = disable
 }

socket.js

@@ -130,6 +130,7 @@ module.exports = function socket (socket) {
           return (noverify = true)
         }
       },
+      keepaliveInterval: socket.request.session.ssh.keepaliveInterval,
       debug: debug('ssh2')
     })
   } else {