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/cancelled-invitation.html

@@ -3,13 +3,13 @@
 {% block maincolumn_content %}
     <div class="govuk-grid-row">
       <div class="govuk-grid-column-two-thirds">
-        <h1 class="heading-large">
+        <h1 class="font-body-2xl margin-bottom-3">
           The invitation you were sent has been cancelled
         </h1>
-        <p class="govuk-body">
+        <p>
           {{ from_user }} decided to cancel this invitation.
         </p>
-        <p class="govuk-body">
+        <p>
           If you need access to {{ service_name or organisation_name }}, you’ll have to ask them to invite you again.
         </p>
       </div>