Updated calls to current Smarty API (register_function()/register_modifier()/register_block() -> registerPlugin(); assign_by_ref() -> assignByRef()).
Fixed file includes in templates with quotes.
Removed SmartyValidate.class.php includes.
Still work in progress as some errors still appear!
Noticed that when editing an entry, the categories checkbox container's
name was 'Archive'. I modified the template and the lang file so that
it's 'Categories' from now on.
