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.
you mean, get them separately on the UI?