Preventing download of a file when it exists
Preventing download of a file when it exists

The DownloadTask will download and append to a file that already exists
and passes MD5.

In order to fix this:
- Check if the file exists
  - If there is no validation hash delete the file
  - If there is a validation hash, check if it matches, if so bypass the
  downloading an additional check

github-for-unity/Unity,github-for-unity/Unity,github-for-unity/Unity