Notify user on sending success

Fixing notification on email sending success. Due to REQ06 we cannot
use popup windows, so there has to be alternative way of notifying
users of email sending success - without refreshing page if possible.
Right context found

Email body should contain information about course and book name; query
in lib.php to extract book data using context; context and course id
have to be sent from block.php file - adding additional arguments to
action link
Poboljšanje lokalizacija

Poboljšanje jezičnih lokalizacija i uvođenje Hrvatske lokalizacije.