add license files
initialize export file with full filepath

addresses ilastik #818
operator.py: fixme comment.
OrderedSignal: Added clean() method
testOpFormattedDataExport: Added an assert
OpH5WriterBigDataset: Flush data immediately after finishing write, and discard h5 file and dataset during cleanUp().
tests: Added some debug output to testOpFormattedDataExport.py