Add a link to directly edit a database list

To support easier editing of database lists, drop in a link at the
bottom of the database list if the logged-in user is a librarian or
administrator.

This will get in the way of merging the two node--database_list
templates, a bit, but oh well. It can be done!

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Merge pull request #4 from dbs/edit_database_lists

Add a link to directly edit a database list