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/works_by_composer.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+
+import '../backend.dart';
+import '../database.dart';
+
+class WorksByComposer extends StatelessWidget {
+  final int personId;
+  final void Function(Work work) onTap;
+
+  WorksByComposer({
+    this.personId,
+    this.onTap,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final backend = Backend.of(context);
+
+    return StreamBuilder<List<Work>>(
+      stream: backend.db.worksByComposer(personId).watch(),
+      builder: (context, snapshot) {
+        if (snapshot.hasData) {
+          return ListView.builder(
+            itemCount: snapshot.data.length,
+            itemBuilder: (context, index) {
+              final work = snapshot.data[index];
+              return ListTile(
+                title: Text(work.title),
+                onTap: () => onTap(work),
+              );
+            },
+          );
+        } else {
+          return Container();
+        }
+      },
+    );
+  }
+}