Added two new filters and missing translations

[baden03]

Added new adverts_back_button and adverts_public_link to change/remove the back/view/preview buttons at the top of the manage-edit template

[gwin]

Thanks i will include it in the next release, but please note that in order to make the filter names more specific in the final release i will change them to:

• adverts_back_button -> adverts_manage_edit_back_button
• adverts_public_link -> adverts_manage_edit_public_link

[baden03]

very good, thank you.