Show book recommendations 

- Calculate book similarities by Pearson correlation coefficient or
Euclidean distance measures (recommendations.clj file)
- On the book page, show maximum 10 similar books.
Insert initial users

- If there are no users in the database, insert users
Fix bugs with pagination and displaying message when there are no books

- When there are no books in the database, pagination is shown
- If no books are found when search criteria is entered, show
information message.