added two aliases to Symfony2 Plugin

plugins/symfony2/symfony2.plugin.zsh

@@ -10,4 +10,8 @@ _symfony2 () {
   fi
 }
 
-compdef _symfony2 app/console
+compdef _symfony2 app/console
+
+#Alias
+alias sf2='php app/console'
+alias sf2clear='php app/console cache:clear'