Remove hard-coded repository URL
- All repository URLs now come from JMS messages (or the reindex servlet's baseURI parameter)

Partial resolution of: https://www.pivotaltracker.com/story/show/72351918
Parsing baseURI and returning 400 Bad Request if blank/invalid/etc.
Merge pull request #50 from fcrepo4/missing-baseURI-error

Parsing baseURI and returning 400 Bad Request if blank/invalid/etc.