Remove unused connection strings (North Central US). The databases have been
removed.
- Checkin in Web.config for setting expiration on static content.
- Modify solution to include book.png, book_cover.png and book_toc.png
Ticket #8: Fix issue where students are able to view the content of courses
they are not registered for.

CR: Arvind.
Fix broken image.
Added support for refreshing and deleting books

Added support for uploading newer versions of the book without having to
restart the server. This requires full support for deleting books from
the database and the blob store cache.