Add the possibility to rename the local files

[GrazianoCapelli]

The remote files must be 8 chars lengthed (and CAP_CHARACTERS), but the local files, in Android filesystem, can be longer and contain more characters, spaces and so on.

It would be fine to have the ability to rename the downloaded files, in order to give to the user the possibility to type a better description of every local file.

[JLJu]

This is overengineering!
Nevertheless, I like it.