Added isEnabled parameter && argument to disable method

Author: Dmitry Drozd

src/Form.php

@@ -83,9 +83,9 @@ public function view()
         ]);
     }
 
-    public function disable()
+    public function disable($disabled = true)
     {
-        $this->disabled = true;
+        $this->disabled = $disabled;
 
         return $this;
     }
@@ -95,6 +95,11 @@ public function isDisabled()
         return $this->disabled;
     }
 
+    public function isEnabled()
+    {
+        return !$this->disabled;
+    }
+
     public function render()
     {
         $this->setupFormName();