Update h1 on pill pages to work with new pill

Pill pages are:
- /notifications
- /template-usage
- /monthly
- /organisations/<organisation_id>
- /templates

Includes changes to:
- the folder-path component
- the page-header component

...all their h1s have the same id.

app/templates/views/dashboard/all-template-statistics.html

@@ -1,3 +1,4 @@
+{% from "components/page-header.html" import page_header %}
 {% from "components/message-count-label.html" import message_count_label %}
 {% from "components/pill.html" import pill %}
 {% from "components/table.html" import list_table, field, right_aligned_field_heading, row_heading, spark_bar_field %}
@@ -10,7 +11,7 @@
 
 {% block maincolumn_content %}
 
-  <h1 class="heading-large">Templates used</h1>
+  {{ page_header("Templates used") }}
 
   <div class="bottom-gutter-3-2">
     {{ pill(

app/templates/views/dashboard/monthly.html

@@ -1,3 +1,4 @@
+{% from "components/page-header.html" import page_header %}
 {% from "components/big-number.html" import big_number_with_status, big_number %}
 {% from "components/pill.html" import pill %}
 {% from "components/table.html" import list_table, field, hidden_field_heading, right_aligned_field_heading, row_heading %}
@@ -12,9 +13,7 @@
 
 {% block maincolumn_content %}
 
-  <h1 class="heading-large">
-    Messages sent
-  </h1>
+  {{ page_header('Messages sent') }}
   <div class="bottom-gutter">
     {{ pill(
       items=years,

app/templates/views/notifications.html

@@ -1,6 +1,7 @@
 {% extends "withnav_template.html" %}
 {% from "components/ajax-block.html" import ajax_block %}
 {% from "components/message-count-label.html" import message_count_label, recipient_count_label %}
+{% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/textbox.html" import textbox %}
 {% from "components/form.html" import form_wrapper %}
@@ -23,9 +24,7 @@
 
 {% block maincolumn_content %}
 
-  <h1 class="heading-large">
-    {{ page_title }}
-  </h1>
+  {{ page_header(page_title) }}
   {% if not message_type == "letter" %}
 
     {{ ajax_block(

app/templates/views/organisations/organisation/index.html

@@ -1,3 +1,4 @@
+{% from "components/page-header.html" import page_header %}
 {% from "components/big-number.html" import big_number %}
 {% from "components/live-search.html" import live_search %}
 {% from "components/message-count-label.html" import message_count_label %}
@@ -10,9 +11,7 @@
 
 {% block maincolumn_content %}
 
-  <h1 class="heading-medium">
-    Usage
-  </h1>
+  {{ page_header('Usage', size='medium') }}
 
   <div class="bottom-gutter">
     {{ pill(years, selected_year, big_number_args={'smallest': True}) }}

app/templates/views/templates/choose.html

@@ -4,6 +4,7 @@
 {% from "components/textbox.html" import textbox %}
 {% from "components/live-search.html" import live_search %}
 {% from "components/form.html" import form_wrapper %}
+{% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
 
 {% extends "withnav_template.html" %}
@@ -18,9 +19,7 @@
 
   {% if (not current_service.all_templates) and (not current_service.all_template_folders) %}
 
-    <h1 class="heading-medium">
-      {{ page_title }}
-    </h1>
+     {{ page_header(page_title, size='medium') }}
 
      <p class="govuk-body">
        {% if current_user.has_permissions('manage_templates') %}