Adds dummy header with placeholder image and text
Adds row offset (1) to gallery, so we can display 1st item as header
Adds the loading of the correct image in the header.

- might need a new view type for header; or no custom at all, do it all manually
- this is due to thumbnail being loaded and there being no caption for regular galleryitemviews
Adds real caption from galleryitem to header
Adds a minimum wait for manual refresh to prevent excessive API calls