Exporting data from an already exported dataset causes problems if the file name was not changed

[B-Hartmann]

Shape-Out 2.14.1
Windows 10

I exported a dataset into a folder. I didn't change the name of the resulting file. Then I loaded that dataset again and applied another filter. I tried to export the filtered data into the same location, getting a PermissionError. It seems that Shape-Out always tries to name the new file SO2-export_0_+sample name+.rtdc and if that file already exists, it cannot create a new file or override the old one because that file is processed in Shape-Out.

Unhandled exception in Shape-Out version 2.14.1:
Traceback (most recent call last):
  File "shapeout2\gui\export\e2data.py", line 46, in done
    self.export_data()
  File "shapeout2\gui\widgets\wait_cursor.py", line 31, in wrapper
    ret = func(*args, **kwargs)
  File "shapeout2\gui\export\e2data.py", line 89, in export_data
    ds.export.hdf5(
  File "dclab\rtdc_dataset\export.py", line 227, in hdf5
  File "pathlib.py", line 1206, in unlink
PermissionError: [WinError 32] Der Prozess kann nicht auf die Datei zugreifen, da sie von einem anderen Prozess verwendet wird: 'C:\\Users\\bhartma\\Desktop\\SO2-export_0_SampleName.rtdc'

Suggestion:
Make Shape-Out check if the destination folder already contains a .rtdc file which starts with SO2-export_0_ and increase the number at the end of this string (1, 2, ...). That would also help to prevent accidentally overriding a previously exported file. Right now, when I export data filtered with one filter, then deactivate that filter and activate a second filter and export the dataset again into the same location, the file that was exported first gets overridden.

[B-Hartmann]

This is at least true for datasets from the same sample folder (and hence the same sample name in the metadata section).

[B-Hartmann]

Maybe a starting point for #152 or #137 ?