[LMS-1708] Add channel labels to screening API

...x/cisd/openbis/dss/etl/AbstractHCSImageFileExtractor.java

.../systemsx/cisd/openbis/dss/etl/HCSImageFileExtractor.java

.../systemsx/cisd/openbis/dss/etl/PlateStorageProcessor.java

...x/cisd/openbis/dss/etl/dynamix/HCSImageFileExtractor.java

.../openbis/dss/screening/server/DssServiceRpcScreening.java

...gin/screening/shared/api/v1/dto/ImageDatasetMetadata.java

...plugin/screening/shared/basic/dto/ChannelDescription.java

...ugin/screening/shared/basic/dto/PlateImageParameters.java

...bis/plugin/screening/shared/imaging/HCSDatasetLoader.java

...screening/shared/imaging/dataaccess/IImagingQueryDAO.java

...ning/client/api/v1/ScreeningOpenbisServiceFacadeTest.java

...eening/shared/imaging/dataaccess/ImagingQueryDAOTest.java