Make the 'page' setting for entity view useful again

Entity view returns the build array, so Option 2 still let the caller decide, but Option 1 seems less confusing. Maybe the two could be done and optional, one overriding the other.

I agree that ideally the caller should be able to decide upon this.
With option2 one might end up with viewing in page-module if people re-use the view mode somewhere else, e.g. from a view. In most cases that's probably unwanted behaviour then, so let's require $page to be explicitly set (option1)

@patch:
* Problem is entity_view() also serves as harmonized entity_view() for core entities, where this option does not exist. So we'll need to document that this option only works for entities provided via the EntityAPIControllerInterface.
* Also, we need to document the default behaviour of guessing if NULL "is passed".
* It's a bit unfortunate to have another API change, but most people should use or extend the provided controller anyway - beside you.. ;) So I guess it should be ok.

For d8, I think we should migrate entity_view() to take a $options array like many other functions.

Thanks, committed.

-> We have an API Change for EntityAPIControllerInterface::view():

Modules that override the method of the default controller or implement the interface themselves have to follow the following change:

-  public function view($entities, $view_mode = 'full', $langcode = NULL) {
-    $view = parent::view($entities, $view_mode, $langcode);
+  public function view($entities, $view_mode = 'full', $langcode = NULL, $page = NULL) {
+    $view = parent::view($entities, $view_mode, $langcode, $page);

AS #1210806: Add corollary to node_is_page() has shown, we forgot adding $page to Entity::view().

Doing so is an API change. However usually modules should override buildContent() not view(), so it should be ok.

Couldn't be more straightforward.

Committed.