This should be the main step in the download refactoring initiated by commit
81a2a06818.
The stub functions introduced by that commit were implemented.
The big download code was mostly composed of two steps, and so it has been
naturally splitted in two functions : download_external and download_internal
file:/// urls are now handled manually, instead of forcing the use of the
internal downloader.
Thanks to Dan for fixing the remaining issues and cleaning up the patch :)
Signed-off-by: Chantry Xavier <shiningxc@gmail.com>