[Commands] Combining commands related to "file" into one command. Similar to the "Excel" command

[JakubMarciniak93]

Perhaps commands like:

• checksum_files,
• clean_files(better name remove or clear?),
• encrypt_files,
• file_convert,
• file_stats,
• find_files,
  It's worth moving it to one command. Example call:
  shellman file checksum
  shellman file clean
  shellman file find

To consider whether it's worth it.

[Remember to update help and README.md]