Added Presets to Indexers

The logic also exists for DownloadClients and Notifications, but they don't show coz there aren't any default definitions.
Also added a Info Link button linking to the wiki pages.

Please pay special attention to the SchemaBuilder change, I effectively use the preset to copy any default values that don't have a FieldDefinition, so anything that doesn't get sent to the UI.
Not sure I like that approach, I think it would be better to get the definition and the defaults as separate methods, since they are separate things (on is based on another).