Update Topic get_absolute_url method.

[akatsoulas]

• Simplify breadcrumb construction in wiki.

[escattone]

r+wc

I think the following two calls to get_absolute_url() should include the product slug as well, so something like get_absolute_url(product.slug)?

• kitsune/kitsune/products/jinja2/products/documents.html

  Line 13 in dbc2565

  {% set canonical_url = canonicalize(model_url=subtopic.get_absolute_url()) %}

• kitsune/kitsune/products/jinja2/products/documents.html

  Line 17 in dbc2565

  {% set canonical_url = canonicalize(model_url=topic.get_absolute_url()) %}