(Updated) Tidying... move export and import functions to common functions +

[Pringleman83]

The import json and export json functions in football.py need to be moved to the common functions file. This will involve making sure that they are properly referenced when called.

The import and export functions will also need to be ask the user for a filename to save to. For the export function (which currently accepts a filename argument), this will mean reducing the number of arguments taken and therefore altering any code that calls the function.

Any questions, comment or get in touch on Slack.

[Pringleman83]

All done.