Clarifyng labels in the proper way.

Added contextual markers as @mbertheau suggested here: https://github.com/tangentlabs/django-oscar/pull/1353
I found the line that seems a bit strange for me: https://github.com/tangentlabs/django-oscar/blob/master/oscar/templates/oscar/dashboard/catalogue/product_list.html#L81
Originally, it was
``` 
{% anchor 'title' _("Title") %}
```
that looks some mmm... hackish, didnt it?