Add recording selector

As a proof of concept some widgets were seperated. The home screen now
links to this instead of the recording editor.

lib/widgets/ensemble_text.dart

@@ -0,0 +1,26 @@
+import 'package:flutter/material.dart';
+
+import '../backend.dart';
+import '../database.dart';
+
+class EnsembleText extends StatelessWidget {
+  final int ensembleId;
+
+  EnsembleText(this.ensembleId);
+
+  @override
+  Widget build(BuildContext context) {
+    final backend = Backend.of(context);
+
+    return StreamBuilder<Ensemble>(
+      stream: backend.db.ensembleById(ensembleId).watchSingle(),
+      builder: (context, snapshot) {
+        if (snapshot.hasData) {
+          return Text(snapshot.data.name);
+        } else {
+          return Container();
+        }
+      },
+    );
+  }
+}