Parse and use DMOZ titles/summaries

[sylvinus]

We current download the DMOZ data but we only store a boolean signal for the presence of URLs or domains in their dumps.

We should start storing titles and descriptions, and then use them as fallbacks in the search results. An example where this would help is commonsearch/cosr-results#3

We should also add support for <META NAME="ROBOTS" CONTENT="NOODP"> as explaned here: http://sitemaps.blogspot.com/2006/07/more-control-over-page-snippets.html

A few pointers:

• Plug into format_title and format_summary using url_metadata : https://github.com/commonsearch/cosr-back/blob/master/cosrlib/formatting.py
• Add some tests! https://github.com/commonsearch/cosr-back/blob/master/tests/cosrlibtests/test_formatting.py

[sylvinus]

Since #26 we store title + description in the URLServer so this got much easier!