UI Extensibility

NaroCAD extensibility was made to extend it as shapes. But sometimes is useless without adding your custom interface to call in this new functionality. This functionality is here. Some problems are still there. The biggest one is that the NaroCAD is not aware of plugins loaded so every time you reload the plugin, the new UI will be added again and again. But just restarting NaroCAD will make everything to go to defaults, so probably you will not have problems as long you extend.