adapted AbstractFileStoreURIPortObject to new FileStorePortObject
implemented FileStoreReferenceURIPortObject that holds references on other port objects instead of managing it's own files
FileMerger now also uses FileStoreReferenceURIPortObject
fixed duplication error introduced with rebase
set package requirement to 2.10
Merge branch 'develop' into feature/knime-2_10
added dependency to core, limited to < 2.10 since api changes with 2.10
Merge branch 'release/0.8.0' into develop
Merge branch 'develop' into feature/knime-2_10
fixed dependency issue
Merge branch 'feature/knime-2_10' into develop