Add control code preview generation

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/control_codes/control_codes.py

@@ -0,0 +1,15 @@
+from __future__ import unicode_literals
+
+from .classes import ControlCode
+
+
+class ControlCodeTest(ControlCode):
+    arguments = ('argument_1',)
+    label = 'Test'
+    name = 'test'
+
+    def execute(self):
+        pass
+
+
+ControlCode.register(control_code=ControlCodeTest)