Add `split-nxfile` application.

reason

can become a useful tool to debug / go around some bugs / minor issues some time. Better than to ask people to write their own piece of code and not much as we can reuse existing classes.

example of usage

nxtomomill split-nxfile /data/projects/whaitiri/Data/JULY_2022/VCT5A_FT_H_Exp3/Scan.nx part_{index}.nx

documentation

ts/nxtomomill$ python3 -m nxtomomill split-nxfile --help
usage: nxtomomill split-nxfile [-h] [--overwrite] [--duplicate-data [DUPLICATE_DATA]] input_file [output_file_pattern]

split a file containing several NXtomo (at root level) into multiple files containing each a single NXtomo

positional arguments:
  input_file            File containing NXtomo to be split into several files
  output_file_pattern   output file pattern. Must contain `{entry_name}` or `{index}` pattern to make sure it is unique

optional arguments:
  -h, --help            show this help message and exit
  --overwrite           Do not ask for user permission to overwrite output files
  --duplicate-data [DUPLICATE_DATA]
                        Make all NXtomo free of any external link. As a result this will duplicate data

close #148 (closed)