Remove tabs UI from code editor and move to plugin. Enhance plugin system.

- Remove tabs controller, tab widget, and tabs widget files and move to plugin
- Delete plugins/README.txt
- Add register_controller method to controller system for plugin use
- Add error handling for plugin crashes via futures callback

src/libs/controllers/controller_base.py

@@ -39,3 +39,6 @@ class ControllerBase(Singleton, EmitDispatcher):
     def message_to_selected(self, names: list[str], event: BaseEvent):
         for name in names:
             self.controller_context.message_to_selected(name, event)
+
+    def register_controller(self, name: str, controller):
+        self.controller_context.register_controller(name, controller)

src/libs/controllers/controller_context.py

@@ -25,3 +25,6 @@ class ControllerContext:
 
     def message_to_selected(self, name: list, event: BaseEvent):
         raise ControllerContextException("Controller Context 'message_to_selected' must be overriden by Controller Manager...")
+
+    def register_controller(self, name: str, controller):
+        raise ControllerContextException("Controller Context 'register_controller' must be overriden by Controller Manager...")

src/libs/controllers/controller_manager.py

@@ -22,9 +22,10 @@ class ControllerManager(Singleton, dict):
 
 
     def _crete_controller_context(self) -> ControllerContext:
-        controller_context             = ControllerContext()
-        controller_context.message_to  = self.message_to
-        controller_context.message     = self.message
+        controller_context                     = ControllerContext()
+        controller_context.message_to          = self.message_to
+        controller_context.message             = self.message
+        controller_context.register_controller = self.register_controller
 
         return controller_context