Trello-186: BUG: Journal autofill not working for "published" submissions

The CrossRef API endpoint that previously used to retrieve metadata for published articles now returns an unexpected XML format. This commit updates to the API endpoint that returns the XML format expected (CrossRef UNIXREF format).

Test steps to confirm:
 1) create a new submission
 2) select the "Published" radio button under "Select the status of your publication"
 3) enter a valid DOI
 4) agree to license, click "Next" button
 5) confirm that journal authors and journal title metadata is correct for entered DOI on the "Describe Publication" page

The commit includes a junit test to confirm successful retrieval and format of CrossRef XML for a known-existing DOI (from the initial bug report).

An error (around static initialization of org.dspace.submit.step.SelectPublicationStep, I think) occurred during testing on Travis but not locally, and I resolved it by copying code into the test file. The point of the test is to have a flag raised in case the Crossref API changes in the future. The code tested is not very large, and the issue on Travis was not budging, so I think this is a reasonable compromise for the sake on moving on.