- Removed links to the gov uk stylesheets

- Deleted /stylesheets folder
- Removed sass build from gulpfile
- Changed gov links to usa links
- Changed other govuk styles, like breadcrumbs
- Changed name of uk_components file to us_components
- Fixed a few tests that broke on account of the changes

app/templates/views/platform-admin/_base_template.html

@@ -3,11 +3,11 @@
 
 {% block main %}
 <div class="govuk-width-container {{ mainClasses }}">
-    <div class="navigation-service">
-      <div class="navigation-service-name govuk-!-font-weight-bold">
+    <div class="navigation-service usa-breadcrumb">
+      <div class="navigation-service usa-breadcrumb-name govuk-!-font-weight-bold">
         Platform admin
       </div>
-      <a href="{{ url_for('main.choose_account') }}" class="govuk-link govuk-link--no-visited-state navigation-service-switch">Switch service</a>
+      <a href="{{ url_for('main.choose_account') }}" class="usa-link navigation-service usa-breadcrumb-switch">Switch service</a>
     </div>
     <div class="grid-row">
       <div class="tablet:grid-col-2">
@@ -27,7 +27,7 @@
             ('Clear cache', url_for('main.clear_cache')),
           ] %}
             <li>
-              <a class="govuk-link govuk-link--no-visited-state" href="{{ url }}">
+              <a class="usa-link" href="{{ url }}">
                 {{ link_text }}
               </a>
             </li>