add module system and move sensor into core with it

src/layout/widgets.rs

@@ -14,8 +14,6 @@ pub struct WidgetData {
     pub label: String,
     /// dynamic borrow checking
     pub borrowed: bool,
-    /// whether this widget has any sensors
-    pub sensor: bool,
 }
 
 impl Widgets {
@@ -85,7 +83,6 @@ impl Widgets {
                 widget,
                 label,
                 borrowed: false,
-                sensor: false,
             },
         );
     }