cleanup of duplicate POE OSV files with different publication date

[johntruckenbrodt]

The S1.OSV tool will download a POE file if it does not exist locally. For comparison the start and stop range are not considered, but rather only the file name is used. This is intended as it makes it possible to download new files in case OSV info has been re-published. However, currently both files will be kept, e.g.

• S1A_OPER_POEORB_OPOD_20151122T122516_V20151101T225943_20151103T005943.EOF.zip
• S1A_OPER_POEORB_OPOD_20210309T091152_V20151101T225943_20151103T005943.EOF.zip

Optimally the file that was published earlier, which is now obsolete, will be deleted. A cleanup routine is needed, which is started upon instantiation of an OSV object (similar to the RES file cleanup) or right after download of the new file.