Adds ability to upload avatar files to High Fidelity for hosting, including marketplace certificates. Goal is to make it easy to bring custom avatars into the world without needing to provide your own hosting for their files. Marketplace certificate will allow authenticity to be established, and you will not be able to wear an avatar hosted in this way unless you are the original uploader.

Note that you can still host avatar files at other locations - hosting by High Fidelity will be an option, not a requirement.