Save the Account page filter setting to the state file

Use the newly created functions to save and restore the account filter
settings to the saved 'Account Hierarchy' section of the state file.

gnucash/gnome/gnc-plugin-page-account-tree.c

@@ -759,6 +759,10 @@ gnc_plugin_page_account_tree_create_widget (GncPluginPage *plugin_page)
                            gnc_plugin_page_account_tree_summarybar_position_changed,
                            page);
 
+    // Read account filter state information from account section
+    gnc_tree_view_account_restore_filter (GNC_TREE_VIEW_ACCOUNT(priv->tree_view), &priv->fd,
+       gnc_state_get_current(), gnc_tree_view_get_state_section (GNC_TREE_VIEW(priv->tree_view)));
+
     LEAVE("widget = %p", priv->widget);
     return priv->widget;
 }
@@ -782,6 +786,10 @@ gnc_plugin_page_account_tree_destroy_widget (GncPluginPage *plugin_page)
                                  gnc_plugin_page_account_tree_summarybar_position_changed,
                                  page);
 
+    // Save account filter state information to account section
+    gnc_tree_view_account_save_filter (GNC_TREE_VIEW_ACCOUNT(priv->tree_view), &priv->fd,
+       gnc_state_get_current(), gnc_tree_view_get_state_section (GNC_TREE_VIEW(priv->tree_view)));
+
     // Destroy the filter override hash table
     g_hash_table_destroy(priv->fd.filter_override);