Handle multiplatform shared folder for downloads

[iLLiCiTiT]

Current Behavior:

Addon is downloading files to single directory, but does not expect that the destination directory is shared for multiple platform.

At the same time downloading of the files should be able to detect if different process/machine is downloading the same files too.

Expected Behavior:

We should be able to handle platform and store the downloaded content per platform, or some hash. And use e.g. lock files, or move content to final destination after download and unpack to avoid concurency from different process/machine.

[iLLiCiTiT]

Platform specific folders were solved by #20 but we still should make sure that multiple processes don't try to download the same file and extract it to same folder at the same time.