Improve routing of "/robots.txt", "/favicon.ico", and "/status/" on Short and Blog sites

Summary: Ref T13636. Add routing for "/robots.txt", "favicon.ico", and "/status/" on the ShortSite and BlogSite.

Test Plan: Visted all resources (and 404 pages) on Short and Blog sites, and Platform site.

Maniphest Tasks: T13636

Differential Revision: https://secure.phabricator.com/D21607