Admin Download edit view changes

[razvanaldea89]

• Hide the Short description metabox if the active custom template doesn't have the short description functionality in it ( do it from the Screen Options ).
• Remove the Paid only checkbox if the Download has been attached to a product. Still show a visual indicator that the Download has a lock mechanism that only paying customers can download its files.
• Move the "Amazon S3 and Google Drive" upsells out from the metabox and into their own metabox, and let the Versions metabox more freely

[TeoAlex]

The "Amazon S3 and Google Drive" upsells are in their own metabox

[cristinnaiulia]

• short description functionality was disable by default, you can enable it from screen options
• paid only checkbox was removed if the Download has been attached to a product
• the "Amazon S3 and Google Drive" upsells are in their own metabox