Create the files path based on the date of creation

[david-caro]

Currently we are using the following path structure (https://github.com/inveniosoftware/invenio-files-rest/blob/master/invenio_files_rest/helpers.py#L207):

base_uri/XX/YY/ZZZZ-ZZZZ-ZZZZ-ZZZZ-ZZZZZZZZZZZZ/data

Where XXYYZZZZZZ-ZZZZ-ZZZZ-ZZZZ-ZZZZZZZZZZZZ is the uuid of the file object. In order to help with the archival of the files, we should adapt it to a date based one, something like:

base_uri/YYYY/MM-wWW/ZZZZ-ZZZZ-ZZZZ-ZZZZ-ZZZZZZZZZZZZ/data

Where YYYY is the year, MM is the month, WW is the week number and ZZZZ-ZZZZ-ZZZZ-ZZZZ-ZZZZZZZZZZZZ the uuid of the file object.

[david-caro]

I created this issue in this repo because currently it's where that path is generated.

@lnielsen please add/correct anything I might have messed up.

[david-caro]

Related to inveniosoftware/invenio-xrootd#20