[Release] v4.2.0+40200006 (#296)

TWEAKS
- [Sonarr/Upcoming] If an episode has not aired, show it as "Upcoming" instead of "Not Downloaded"

FIXES
- [Accounts] Register device token to database for future notification support
- [Accounts] Improve validation for email and passwords
- [Radarr] Fix some durations being displayed twice
- [UI/TextField] Show errors as snackbar instead of in-line error

lib/core/ui/sticky_header.dart

@@ -1,23 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:flutter_sticky_header/flutter_sticky_header.dart';
-
-class LSStickyHeader extends StatelessWidget {
-    final List<Widget> children;
-    final Widget header;
-
-    LSStickyHeader({
-        @required this.header,
-        @required this.children,
-    });
-
-    @override
-    Widget build(BuildContext context) => SliverStickyHeader(
-        header: header,
-        sliver: SliverPadding(
-            sliver: SliverList(
-                delegate: (SliverChildListDelegate(children)),
-            ),
-            padding: EdgeInsets.symmetric(vertical: 8.0),
-        ),
-    );
-}