Updating site to use USWDS styles (#509)

* Updated header and footer
* Updated fonts
* Moved files around and updated gulpfile to correct the build process when it goes to production
* Adjusted grid templating
* Added images to assets
* Update app/templates/components/uk_components/footer/template.njk

Co-authored-by: Steven Reilly <stvnrlly@users.noreply.github.com>

app/templates/views/service-settings/set-email.html

@@ -17,7 +17,7 @@
   <div class="govuk-grid-row">
     <div class="govuk-grid-column-five-sixths">
       {{ page_header('Send emails') }}
-      <p class="govuk-body">
+      <p>
         It’s free to send emails through U.S. Notify.
       </p>
       {% call form_wrapper() %}