Improving collection management interface

Tidying up collection contents management.

You should be able to remove items based on your privileges on the
collection -- not your privileges on the contained item.

Allow collection edit controls to be in the page header

Allow AJAX removal of collection members

Fixes ndlib/planning#332

View test hooks and refactoring

Data attributes to the rescue. In the future we could use these for
JavaScript behavior too.

Let people rename their profile collection.

This may be a bad idea.

Only let items be removed from collections on the collection page.