Added mail helper methods to tests
Using field_name for field storage in sync test
changed subscription block msg txt
Merge branch '8.x-1.x' of github.com:iwanfux/simplenews into 8.x-1.x
cleaned up .module and admin.inc; fixed tests
ButtonsWidget moved to OptionsButtonsWidget
Use getId() instead of ->id for current language, fix watchdog() call.
clean up and adding email view modes
clean up and adding email view modes
drupal_add_html_head() removed

Also changed NULL to array() in WebTestBase::drupalPostForm() calls.
Made mail helpers index-based

lastMailBody introduced in abd0c4a was a bad idea because it does not assert
the number of mails sent.
Merge branch '8.x-1.x' into personalization

Conflicts:
	src/Form/SubscriberForm.php
	src/Plugin/Field/FieldWidget/SubscriptionWidget.php
	src/Tests/SimplenewsSubscribeTest.php
	src/Tests/SimplenewsSynchronizeFieldsFormTest.php
	src/Tests/SimplenewsTestBase.php