Uploading non-image media types

[gjcope]

Currently only images are uploaded via inclusion in the article editor. Other media types (videos, etc.) must be embedded from another source. We currently have some infrastructure challenges in supporting uploading and archiving other media, but also understand the utility of it.

@sdumetz has contributed a solution for this if/when we can support it. (#199 ) This issue will serve as a spot to track progress on this support and hear from anyone else who needs this feature.