* add management section to SavedObjectsType
* adapt import/export routes to get types accessor
* add documentation
* update generated doc
* update migration guide
* use request context to access exportable types
* update generated doc
* adapt SavedObjectsManagement to use the registry
* stop magical tricks about the config type, register it as any other so type.
* fix FTR assertions
* fix so_mixin tests
* register the `config` type from the uiSettings service
* nits and comments
* update generated doc
* remove true from dynamic property definition, use force-cast back for config type
* remove obsolete test comment