Filesystem manager

[remilvus]

Description:

Implement a module for saving GTFS files. The exact path where a file is kept should be based on a timestamp from GTFS header. For static file a hash of its content may be used to determine the saving path.

What needs to be done:

• [ ] Module for calculating relevant file properties
• [ ] Module for saving files
• [ ] Tests

Additional remarks:

• [ ] Files are divided into folders by category, year and week.
• [ ] It's impossible to save two copies of one file (name of a file should be based only on its contents)

[remilvus]

Instead of creating a 'Module for calculating relevant file properties', I've put property calculation in the persistence module.