[mm_token] More flexible tokens for working with files

It will be practical to have tokens for each verb (harvest, process, ...) like:

[harvest_filepath] - path of harvested file
[harvest_file_filename] - filename of harvested file (filename which includes extension without path)
[harvest_file_name] - name of the file (no path, no extension)
[harvest_file_extension] - extension of harvested file

Such tokens will bring more flexibility for working with files. Practical use case: #546500: prepending user id to file name?.