Add region management

This adds region management: the user can manage a list of available regions
and for each channel pick a region from that list to apply to messages.

Region discovery from nearby repeaters will be done in a separate PR.

This is a part of the work needed for #120.

lib/l10n/app_localizations_it.dart

@@ -338,6 +338,35 @@ class AppLocalizationsIt extends AppLocalizations {
   @override
   String get settings_radioSettingsUpdated => 'Impostazioni radio aggiornate';
 
+  @override
+  String get settings_regionSettings => 'Regions';
+
+  @override
+  String get settings_regionSettingsSubtitle => 'Manage stored regions';
+
+  @override
+  String get settings_regionManagement_screenTitle => 'Region Management';
+
+  @override
+  String get settings_regionNameHint => 'Enter region name';
+
+  @override
+  String get settings_regionAddRegion => 'Add region';
+
+  @override
+  String get settings_regionName => 'Region Name';
+
+  @override
+  String get settings_regionDeleted => 'Region deleted';
+
+  @override
+  String get settings_deleteRegion => 'Delete Region';
+
+  @override
+  String settings_deleteRegionConfirm(String region) {
+    return 'Remove \"$region\" from region list?';
+  }
+
   @override
   String get settings_location => 'Posizione';
 
@@ -1236,6 +1265,20 @@ class AppLocalizationsIt extends AppLocalizations {
   @override
   String get channels_hashtagHint => 'es. #team';
 
+  @override
+  String channels_regionSetTo(String region) {
+    return 'Region: $region';
+  }
+
+  @override
+  String get channels_regionNotSet => 'Region: none';
+
+  @override
+  String get channels_regionSelect_Title => 'Select a region';
+
+  @override
+  String get channels_clearRegion => 'Clear region';
+
   @override
   String get chat_noMessages => 'Nessun messaggio ancora';