Add plugin updating capability

src/main/scala/plugin/PluginSystem.scala

@@ -106,6 +106,28 @@ object PluginSystem {
     }
   }
 
+  /**
+   * Checks whether the plugin is updatable.
+   */
+  def isUpdatable(oldVersion: String, newVersion: String): Boolean = {
+    if(oldVersion == newVersion){
+      false
+    } else {
+      val dim1 = oldVersion.split("\\.").map(_.toInt)
+      val dim2 = newVersion.split("\\.").map(_.toInt)
+      dim1.zip(dim2).foreach { case (a, b) =>
+        if(a < b){
+          return true
+        } else if(a > b){
+          return false
+        }
+      }
+      return false
+    }
+  }
+
+
+
   // TODO This is a test
 //  addGlobalMenu("Google", "http://www.google.co.jp/", "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAAAAYCAYAAADgdz34AAAABHNCSVQICAgIfAhkiAAAAAlwSFlzAAAEvwAABL8BkeKJvAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAAIgSURBVEiJtdZNiI1hFAfw36ORhSFFPgYLszOKJAsWRLGzks1gYyFZKFs7C7K2Y2XDRiwmq9kIJWQjJR9Tk48xRtTIRwjH4p473nm99yLNqdNTz/mf//+555x7ektEmEmbNaPs6OkUKKX0YBmWp6/IE8bwIs8xjEfEt0aiiJBl6sEuXMRLfEf8pX/PnIvJ0TPFWxE4+w+Ef/Kzbd5qDx5l8H8tkku7LG17gH7sxWatevdhEUoXsjda5RnDTZzH6jagtMe0lHIa23AJw3iOiSRZlmJ9mfcyfTzFl2AldmI3rkbEkbrAYKrX7S1eVRyWVnxhQ87eiLjQ+o2/mtyve+PuYy3W4+EfsP2/TVGKTHRI+Iz9Fdx8XOmAnZjGWRMYqoF/4ESW4hpOYk1iZ2WsLjDUTeBYBfgeuyux2XiNT5hXud+DD5W8Y90EtifoSfultfjx7MVtrKzcr8No5m7vJtCLx1hQJ8/4IZzClpyoy5ibsYUYQW81Z9o2jYgPeKr15+poEXE9+1XF9WIkOaasaV2P4k4pZUdDbEm+VEQcjIgtEfGxlLIVd/Gs6TX1MhzQquU3HK1t23f4IsuS94fxNXMO/MbXIDBg+tidw5yMbcCmylSdqWEH/kagYLKWeAt9Fcxi3KhhJuXq6SqQBMO15NDalvswmLWux4cbuToIbMS9BpJOfg8bm7imtmmTlVJWaa3hpnU9nufziBjtyDHTny0/AaA7Qnb4AM4aAAAAAElFTkSuQmCC")
 //    { context => context.loginAccount.isDefined }