re-integrate fixes and improvements from S99.x

fix: NPE on IBM J9 JRE (r19757)
fix: NPE on accessing content that the provider can't povide (r19758)
add: option to disable NIO selector-based sockets in DSS and make them the default (use 'use-nio-selector-socket = true' to enable) (r19759, r19761)
add: some interfaces and annotation classes to screening api that are not needed by Oracle HotSpot JRE but by IBM J9 JRE (r19760)
extend: public screening API: (r19762)
add: methods to IScreeningOpenbisServiceFacade:
listExperiments(String userId),
convertToWellPositions(List<WellIdentifier> wellIds)
createPlateImageReferences(...)
loadImages(List<PlateImageReference> imageReferences, boolean convertToPNG, IPlateImageHandler plateImageHandler)
loadImages(List<PlateImageReference> imageReferences, ImageSize thumbnailSizeOrNull, IPlateImageHandler plateImageHandler)
loadThumbnailImages(List<PlateImageReference> imageReferences, IPlateImageHandler plateImageHandler)
loadThumbnailImages(List<PlateImageReference> imageReferences, final IImageOutputStreamProvider outputStreamProvider)
add: methods to ImageDatasetMetadata:
getTilesRows()
getTilesCols()
getThumbnailHeight()
getThumbnailWidth()
hasThumbnails()

SVN: 19790