Metadata Retrieval: Individual handling of retrieval warnings

[jwiesel]

Sample warnings

• Entity of type 'Layout' named 'XY Layout' cannot be found
• Entity of type 'QuickAction' named 'XYZ' cannot be found
• Cannot retrieve documents in a user's private folder; move the document to a named folder
• Metadata API received improper input. Please ensure file name and capitalization is correct. Load of meta data from db failed for metadata of type:AppMenu and file name:AppSwitcher