/site/events: add pagination

[php-coder]

Improvement for #248

Possible useful links:

• http://getbootstrap.com/components/#pagination
• https://www.javacodegeeks.com/2013/03/implement-bootstrap-pagination-with-spring-data-and-thymeleaf.html
• http://blog.fawnanddoug.com/2012/05/pagination-with-spring-mvc-spring-data.html

[php-coder]

For the history: here is an explanation about createItems() in Russian: c6f7520#commitcomment-18272098