Code cleanup in PGDOIDatabaseTest

Converted many fields to public static final
Added comment about verifyDOIInFile() purpose
Remove DOIDatabase from spring startup
Remove reference to doi.db file in MinterTest
Remove doi.db (and copy) from doi test resources
Remove doi.db.fspath from dspace.cfg
Add @deprecated to DOIMigrator
Fix class used in DOI Logger
Delete DOIDatabase and DOIMigrator

These are the only two classes that depend on doi.db
Merge remote-tracking branch 'origin/doidb-postgres-cleanup' into dryad-master