Add person screen

This just displays a list of the persons works for now. It can be
reached from the home screens list of persons.

lib/screens/person.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/material.dart';
+
+import '../backend.dart';
+import '../database.dart';
+
+class PersonScreen extends StatelessWidget {
+  final Person person;
+
+  PersonScreen({
+    this.person,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final backend = Backend.of(context);
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('${person.firstName} ${person.lastName}'),
+      ),
+      body: StreamBuilder<List<Work>>(
+        stream: backend.db.worksByComposer(person.id).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),
+                );
+              },
+            );
+          } else {
+            return Container();
+          }
+        },
+      ),
+    );
+  }
+}