Add a new endpoint for managing a folder, use it to rename folder

- Add a GET / POST view: manage template folder
- Add a template for that view, where a user can rename their
folder
- Add an API client method for updating a folder

- Test the new feature, including the test that service without
permissions cannot manage a folder

app/navigation.py

@@ -172,6 +172,7 @@ class HeaderNavigation(Navigation):
         'letter_jobs',
         'link_service_to_organisation',
         'manage_org_users',
+        'manage_template_folder',
         'manage_users',
         'monthly',
         'new_password',
@@ -310,6 +311,7 @@ class MainNavigation(Navigation):
             'copy_template',
             'delete_service_template',
             'edit_service_template',
+            'manage_template_folder',
             'send_messages',
             'send_one_off',
             'send_one_off_step',
@@ -625,6 +627,7 @@ class CaseworkNavigation(Navigation):
         'link_service_to_organisation',
         'live_services',
         'manage_org_users',
+        'manage_template_folder',
         'manage_users',
         'monthly',
         'new_password',
@@ -857,6 +860,7 @@ class OrgNavigation(Navigation):
         'letter_jobs',
         'link_service_to_organisation',
         'live_services',
+        'manage_template_folder',
         'manage_users',
         'monthly',
         'new_password',