Downloads API doc

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Further changes to the downloads tutorial

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Fixed spelling of link url

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Sample extension for the downloads API

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>