Drag-drop file upload.

Summary:

• have files be uploaded by drag+drop instead of browse.
• Files are named by their uploaded filename, the user isn't given a chance to enter a file name. Is this bad?
• Store author PHID now with files
• Allow an ?author=<username> to limit the /files/ list by author.
• If one file is uploaded, the user is taken to its info page.
• If several are uploaded, they are taken to a list of their files.

Test Plan:

• Quickly tested everything and it still worked, I'd recommend some people try this out before it gets committed though. It's a rather huge revision.

Reviewers:
epriestley, Ttech

CC:

Differential Revision: 612