implemented the ability to make inputs that can't be connected

app/node/param.h

@@ -266,6 +266,9 @@ public:
    */
   bool IsConnected();
 
+  bool IsConnectable() const;
+  void SetConnectable(bool connectable);
+
   /**
    * @brief Return a list of edges (aka connections to other nodes)
    *
@@ -387,6 +390,11 @@ private:
    */
   QString id_;
 
+  /**
+   * @brief Internal connectable value
+   */
+  bool connectable_;
+
 };
 
 #endif // NODEPARAM_H