Image improvements and redirects

Closes #19 (closed), Closes #31 (closed)

• local copies of logos (DLG, GALILEO, UGA libs, DPLA)
• standardize svg logo height at "50" (so they don't look giant if CSS fails to load; the rendered height if the styles load normally hasn't changed)
• similarly, standardize the height of the social icons at 36 (again, only matters if CSS fails to load)
• add redirects for /ocr -> /about/ocr, /participate -> /about/participate
• add redirects for some built-in openoni place-related routes to our own versions (e.g. /titles/places/georgia/fulton -> /counties/fulton). We may do more on this later, e.g., change all references to the former route so we don't even need a redirect. See issue #33 (closed)