[LMS-2098] use the new image_readers API in 'datastore_server' and 'screening' modules

datastore_server/build/build.xml

...emsx/cisd/openbis/dss/generic/shared/utils/ImageUtil.java

.../cisd/openbis/dss/generic/shared/utils/ImageUtilTest.java

screening/.classpath

...sd/openbis/dss/etl/biozentrum/ImageMetadataExtractor.java

...ugins/DynamixWellBrightnessEqualizerProcessingPlugin.java

...penbis/dss/etl/biozentrum/ImageMetadataExtractorTest.java

...java/ch/systemsx/cisd/openbis/dss/etl/biozentrum/demo.tif

...nbis/dss/screening/server/DssServiceRpcScreeningTest.java