Implement pagination support

[sblinch]

Paginates the book, author, and series lists, and the search results. This should help with browsing large libraries.

I'm aware that you're refactoring the server code, so I tried to keep the changes in server.go as unobtrusive as possible. Basically just an extra .Take() and .Skip() call on each slice, a call to NewPagination(), and an extra variable passed to the template renderer.

Implements #46.