Add collection title to upload form

In the case where you're uploading something from a collection detail
view, you get directed to a link like this:
    http://localhost:8000/upload/?collection=28

Instead of displaying a blank "Collection:" label with no dropdown, we
can show the collection title here.
Merge pull request #21 from nikolas/add-collection-title-to-upload-form

Add collection title to upload form