Added model and database support for EJournals #26

Added case classes EJournalPublisher, EJournal
Added database methods for retrieving, adding, removing publishers and ejournals
Added routes for ejournals under /links/ejournals
    Added model and database support for EBooks #26

    Added case classes EBookPublisher, EBook
    Added database methods for retrieving, adding, removing publishers and ebooks
    Added routes for ebooks under /links/ebooks
    Added model and database support for EDatabases #26

    Added case classes EDatabase
    Added database methods for retrieving, adding, removing edatabases
    Added routes for edatabases under /links/edatabases
Merge pull request #30 from Radsaggi/existing-lists

Existing lists #26