Add file names in the product importer for download files

[mihaijoldis]

Enhancement Request

Explain your enhancement (please be detailed)

At the moment we don't allow setting the File name for a download file when importing. A customer that is going to switch to EDD is trying to import his products (1000+) and he noticed the file names are messy as they are taken based on the File link. For example this is how his import file looks now https://prnt.sc/106uqhr

Did some local work and setting a new field "Download File Names" which should follow the same format like the Links:
Download files in the csv file set to url1.com|url2.com|url3.com and Download File Names set to name1|name2|name3 would allow the user to set his file names directly.

This is from the test I did with 2 download links and setting my own file names https://prnt.sc/106uhmt

Ticket here https://secure.helpscout.net/conversation/1436704679/178575/

[mihaijoldis]

Did some playing locally to try and get something to that customer and this is something that works fine locally https://github.com/mihaijoldis/easy-digital-downloads/tree/feature/file_names