Update to use the selective download based on tag

I have added the function for protecting books based on tag. If you want that I have to change something or edit the languages, let me know.
The files I updated are
- index.php (changed function is_proteced + add defines + globalsettings + add globals from DB)
- lib\BicBucStriim\langs.php
- templates\admin.html

+ second update
I've just changed the title in password dialog box. Language is specific now.

If you have questions, just let me know.