Add a base bulk form handler class

I think the plan of fago is to put actions into the entity system, and get rid of action.module
but until then action_do, which is used by that field, belongs to actions.module.

Shouldn't we just postpone this until there is a proper operations/actions API into core? It's a lot of effort to get both
hook_node_operations hook_user_operations in, to remove it finally anyway?

I agree with #4.

hook_user_operations is a relic and it needs to die.

Green if it's green :)

+++ b/core/modules/system/lib/Drupal/system/Plugin/views/field/BulkFormBase.phpundefined
@@ -35,7 +31,7 @@ public function pre_render(&$values) {
-    if (!empty($this->view->style_plugin) && $this->view->style_plugin instanceof \Drupal\views\Plugin\views\style\Table) {
+    if (!empty($this->view->style_plugin) && $this->view->style_plugin instanceof Table) {

So much better!

+++ b/core/modules/system/lib/Drupal/system/Plugin/views/field/BulkFormBase.phpundefined
@@ -91,7 +81,7 @@ public function views_form(&$form, &$form_state) {
     $form['header'][$this->options['id']]['action'] = array(

I'm wondering whether we should call this action, but yeah operations are somehow similar.

+++ b/core/modules/system/lib/Drupal/system/Plugin/views/field/BulkFormBase.phpundefined
@@ -99,33 +89,22 @@ public function views_form(&$form, &$form_state) {
+  abstract protected function getBulkOptions();

I really like abstract functions as it really helps developers.

+++ b/core/modules/system/lib/Drupal/system/Plugin/views/field/BulkFormBase.phpundefined
@@ -99,33 +89,22 @@ public function views_form(&$form, &$form_state) {
+  abstract public function views_form_submit(&$form, &$form_state);

Just in case someone wonders, camelcase that will be done later, as that is not a new function here.

Committed and pushed to 8.x. Thanks!