R1:221562b29424

Modernize file uploads

Summary:
Modernizes file uploads. In particular:

- Adds a mobile menu, with an "Upload File" item.
- Adds crumbs to the list view, detail view and upload view.
- Adds "Upload File" action to crumbs.
- Moves upload file to a separate page.
- Removes the combined upload file + recent files page.
- Makes upload file use a normal file control by default (works on mobile).
- Home page, file list and file upload page are now global drop targets which accept files dropped…