Taxonomy term template

Refs #3159

* Refactors `dosomething_taxonomy_term_page` to simply return the full view of a taxonomy term, allowing us to make use of built in Taxonomy term template files and preprocess hooks.

* Adds a `taxonomy-term.tpl.php` into the Paraneue theme.
    * Outputs `field_subtitle` in the header
    * Adds inline css to display cover image if set