The release exporter should export more data

[Nicklas Nordborg]

For existing items we should export more annotations/other data:

• Specimen items:
  • If there is an image of the Stained child item with GoodStain=true we should export the image to the release archive. The image should be located in top folder given by external id of the specimen with a filename given by exported HisName annotation + '.jpg' (for example /S000001/S000001.his.jpg). If the image exists in earlier releases it should be linked by symbolic links just as other files are.

We should export more types of items. Some (Lysate, Retract, No and NotAsked) have already been added as part of #1075.