Replace the .column-... classes in _grids.scss

We had 7 classes in _grids.scss named `.column-...` which were being
used to give a certain column width. These worked by using `@include
grid column()`, which is now deprecated.

`.column-whole` and `.column-three-quarters` can be removed and replaced
with `govuk-grid-column-full` and `govuk-grid-column-three-quarters`
respectively. The other column classes don't have a direct replacment in
GOV.UK Frontend. To get round this, we overwrite the `$govuk-grid-width`
SASS map in `extensions.scss` to add in extra widths, then use this with
the `govuk-grid-column` mixin to create new classes in for our custom
widths in `_grids.scss`

app/templates/views/organisations/add-organisation.html

@@ -20,7 +20,7 @@
       <div class="govuk-grid-column-one-quarter">
         &nbsp;
       </div>
-      <div class="column-three-quarters">
+      <div class="govuk-grid-column-three-quarters">
         <main class="govuk-main-wrapper column-main govuk-!-padding-top-0 govuk-!-padding-bottom-0" id="main-content" role="main" >
           {% block beforeContent %}{% endblock %}
           {% block content %}

app/templates/views/organisations/index.html

@@ -23,7 +23,7 @@
           All organisations
         </h1>
       </div>
-      <div class="column-three-quarters">
+      <div class="govuk-grid-column-three-quarters">
 
         {{ live_search(target_selector='.browse-list-item', show=True, form=search_form, label='Search by name') }}
 
@@ -51,7 +51,7 @@
         <div class="govuk-grid-column-one-quarter">
           &nbsp;
         </div>
-        <div class="column-three-quarters">
+        <div class="govuk-grid-column-three-quarters">
           {{ govukButton({
             "element": "a",
             "text": "New organisation",

app/templates/views/organisations/organisation/settings/edit-agreement.html

@@ -15,7 +15,7 @@
     back_link=url_for('.organisation_settings', org_id=current_org.id)
   ) }}
   <div class="govuk-grid-row">
-    <div class="column-five-sixths">
+    <div class="govuk-grid-column-five-sixths">
       {% call form_wrapper() %}
         {{ radios(
           form.agreement_signed,

app/templates/views/organisations/organisation/settings/edit-crown-status.html

@@ -15,7 +15,7 @@
     back_link=url_for('.organisation_settings', org_id=current_org.id)
   ) }}
   <div class="govuk-grid-row">
-    <div class="column-five-sixths">
+    <div class="govuk-grid-column-five-sixths">
       {% call form_wrapper() %}
         {{ radios(form.crown_status) }}
         {{ page_footer('Save') }}

app/templates/views/organisations/organisation/settings/edit-domains.html

@@ -16,7 +16,7 @@
     back_link=url_for('.organisation_settings', org_id=current_org.id)
   ) }}
   <div class="govuk-grid-row">
-    <div class="column-five-sixths">
+    <div class="govuk-grid-column-five-sixths">
       <p>
         If a user’s email addresses ends with one of these domains then
         any services they create will be associated with this organisation.

app/templates/views/organisations/organisation/settings/edit-go-live-notes.html

@@ -15,7 +15,7 @@
     back_link=url_for('.organisation_settings', org_id=current_org.id)
   ) }}
   <div class="govuk-grid-row">
-    <div class="column-five-sixths">
+    <div class="govuk-grid-column-five-sixths">
       <p>
         Text entered here will be displayed in the Zendesk ticket when a service
         belonging to this organisation requests to go live.

app/templates/views/organisations/organisation/settings/edit-name/confirm.html

@@ -16,7 +16,7 @@
   ) }}
 
   <div class="govuk-grid-row">
-    <div class="column-three-quarters">
+    <div class="govuk-grid-column-three-quarters">
 
     {% call form_wrapper() %}
       {{ textbox(form.password, autocomplete='current-password') }}

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

@@ -19,7 +19,7 @@
     {{ user.email_address }}
   </p>
 
-  {% call form_wrapper(class="column-three-quarters") %}
+  {% call form_wrapper(class="govuk-grid-column-three-quarters") %}
       {{ page_footer(
         'Save',
         delete_link=url_for('.remove_user_from_organisation', org_id=current_org.id, user_id=user.id) if user or None,