Have option to create output path automatically + return it

[theroggy]

When writing a GIS analysis geofileops, an uninteresting part of the code is preparing output file names, while most of the time they are really "standard".

Having an automatic way of creating output file names + returning it would be more practical.

I like readable filenames, so ideally there is a logic in how the filenames are created, the only/main disadvantage is that the filenames can become (too!) long...
However, the user needs to still be able to specify a filename, so he can always overrule when the name becomes too long?

[theroggy]

Based on meeting with Sven and Jan:

• Automatic filename generation based on input file(s)
  • if 1 input file, take first 80 chars of input file + operation (eg. "_DISS" for dissolve) + numeric suffix if filename exists already + extension of input file.
  • if 2 input files, take first 40 chars of input1 file + operation (eg. "INTERS" for intersection) + take first 40 chars of input2 file + numeric suffix (eg. "_1") if filename exists already + extension of input file (if one of them is gpkg, gpkg, ortherwise ext of input1)
• directory to use
  • if output_path is None: create tmp dir (%temp%/geofileops_tmp/00001/)+ generate filename as above
  • if output_path is a dir: use the dir + generate filename as above
  • if output_path is a dir: use the path (= current behaviour)

• return output_path in all cases

[theroggy]

Remark: think about what to do with combination of force=True/False versus automatic name creation with existing name...