File uploads should show confirmation

[cwc]

Single-file

• For images, a preview should be displayed. Videos/audio as well if possible. Other file types can just display the filename portion of the source URI.
• Structured input should be provided for extra tags, e.g. 'Add Tag' button -> prompt for tag, stripping commas -> list of tags with X buttons next to them for removal
• Confirm/Cancel buttons

Multi-file

• Initially should display the number of files to be uploaded, perhaps as a breakdown by filetype in the collection (e.g. 'You are uploading: 3 images, 2 videos, 4 audios, 5 others'). Previews could possibly be shown in a scrubber or cover flow type view for filetypes that make sense.
• Same structured input for tags as single-file case, to be applied to all files.
• Should display Cancel/Confirm All and a third button that allows the files to be confirmed individually in a chain, using the single-file UI. This would allow setting tags individually, as well as cancelling the upload for only some of the files.