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.
GetDefaultDefinitions returns the default for all providers, which is always defined. GetPresetDefinitions returns the available presets, which may return an empty list.
Kinda named them similar so you know they're related.
imho GetDefinitions is too easy to confuse with the actual definitions. (Which is actually ```All()```)