Resolves #416 Vacuum support

lib/entities/vacuum/widgets/vacuum_state_button.dart

@@ -0,0 +1,40 @@
+part of '../../../main.dart';
+
+class VacuumStateButton extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    Widget result;
+    VacuumEntity entity = EntityModel.of(context).entityWrapper.entity;
+    if (entity.supportTurnOn && entity.supportTurnOff) {
+      result = FlatServiceButton(
+          serviceDomain: "vacuum",
+          serviceName: entity.state == EntityState.on ? "turn_off" : "turn_on",
+          entityId: entity.entityId,
+          text: entity.state == EntityState.on ? "TURN OFF" : "TURN ON"
+      );
+    } else if (entity.supportStart && (entity.state == EntityState.docked || entity.state == EntityState.idle)) {
+      result = FlatServiceButton(
+          serviceDomain: "vacuum",
+          serviceName: "start",
+          entityId: entity.entityId,
+          text: "START CLEANING"
+      );
+    } else if (entity.supportReturnHome && entity.state == EntityState.cleaning) {
+      result = FlatServiceButton(
+          serviceDomain: "vacuum",
+          serviceName: "return_to_base",
+          entityId: entity.entityId,
+          text: "RETURN TO DOCK"
+      );
+    } else {
+      result = Text(entity.state.toUpperCase(), style: TextStyle(
+          fontSize: 16,
+          color: Colors.grey
+      ));
+    }
+    return Padding(
+      padding: EdgeInsets.only(right: 15),
+      child: result,
+    );
+  }
+}