Add option to keep evidence when suspending accounts

Fix #547

When selected, before the account's data is removed, some of it
is denormalized into a separate, symmetrically-encrypted table. In
particular:

- The e-mail
- All IPs used to access the account
- SHA256 fingerprints of all uploaded files
- URIs of accounts followed by or following the account
- URIs of accounts that were invited

app/views/admin/account_actions/new.html.haml

@@ -1,6 +1,9 @@
 - content_for :page_title do
   = t('admin.account_actions.title', acct: @account.acct)
 
+- content_for :header_tags do
+  = javascript_pack_tag 'admin', integrity: true, async: true, crossorigin: 'anonymous'
+
 = simple_form_for @account_action, url: admin_account_action_path(@account.id) do |f|
   = f.input :report_id, as: :hidden
 
@@ -10,6 +13,9 @@
   - if @account.local?
     %hr.spacer/
 
+    .fields-group
+      = f.input :create_account_summary, as: :boolean, wrapper: :with_label
+
     .fields-group
       = f.input :send_email_notification, as: :boolean, wrapper: :with_label