Copy file to public Downloads directory

[kekkyojin]

PR Checklist

Please check all that apply to this PR using "x":

• [x] I have checked that this PR is not a duplicate of an existing PR (open, closed or merged)
• [x] I have checked that this PR does not introduce a breaking change

PR Type

What kind of change does this PR introduce?

• [x] Bugfix

Fixes

Issue Number: #1095

What is the current behavior?

Explicitly downloaded files are saved to private storage folder

What is the new behavior?

After downloading the file, it will be copied to the generic Donwload or Movies or Images folders depending its mime-type

Other information

Downloaded file will still be on private app-scope storage. It won't be moved to the new folder