Port file attachment views to ES6 and InlineEditorView.
Review Request #1042 - Created Jan. 25, 2018 and updated
This change ports the last couple of file attachment related views (the revision selector view and thumbnail view) to ES6. While I was working on the thumbnail view, I also ported it to use the new InlineEditorView for captions. Testing Done: - Ran js-tests. - Manually tested caption editing in the file attachment thumbnails. Reviewed at https://reviews.reviewboard.org/r/9444/