Make a new image-add pane after each upload [#5]

The change from .change to .on('change') makes the handler apply to new
elements once they're added.
Keep all the test-image filenames in one place

This just reduces duplicated strings...
Tests & fixes for the new-image page [#5]

Hey I think making my markup more test-framework-friendly also made it
more accessible! :)
Functional image-attribute controls in new-image [#5]
Set an album when adding new images [#5]
Create albums on the add-image page [#5]
Don't queue tasks until after committing [#5]

This prevents a subtle race condition where a delayed task starts before
the after_request commit happens, and then fails to find the stuff it
needs in the database.
Upload multiple files at once [#5]

Multiple file uploads do't seem to get useful MIME data, so the
controller can't provide a filetype to new_from_stream any more.

Selenium doesn't seem to support attaching multiple files at once, so
that JS isn't tested. Bogus!

The "file[]" input name seems to be a convention for multiple files,
used by various frameworks including Flask. Note that it messes up
jquery's name selectors since jquery tries to parse the square brackets.