accept individual weights in $args

[gregallensworth]

The intent of DEFAULT_WEIGHTING_TAXONOMY_RATIO is to act as a default value, and that args would have a relevance_scoring structure would give details on the weightings per keyword, per taxo-term, etc.

• [x] score_taxonomy_relevance() should check $args['relevance_scoring']['tax_query'][taxoname] to get a weighting value specifically for that taxonomy; or else use the default

• [x] score_keyword_relevance() should check $args['relevance_scoring']['title_keyword'] and $args['relevance_scoring']['content_keyword'] to get a weighting for those values, or else use the default

[gregallensworth]

Done. Example:

            $filter['relevance_scoring'] = array(
                'tax_query' => array(
                    'policy_topics' => 15.0,
                ),
                'title_keyword' => 1.0,
                'content_keyword' => 0.25,
            );