hard coded strings need replacing with translations

Checked the pages mentioned above continue to work and are appeared properly.

Testing: Check the updated words appear in the relevant pages. Check the pages continue to work.

And more ...
paper/details.php:
// initial link of breadcrumb
$links = array('/' => 'Home');

Documents' search:
"Unassigned" in breadcrumbs is not localised

I've got more:
include/paper_option.php