added stop btn, fixed subscriber count on issue overview and changed some small things
Ultimate Cron config file added
Merge branch '8.x-1.x' into field-sync
removed fieldset from subscription forms and added msg field
Checkout sync form test
Merge branch 'field-sync' into 8.x-1.x
Merge branch '8.x-1.x' into personalization

Conflicts:
	src/Form/SubscriberDeleteForm.php
	src/Form/SubscriberForm.php
	src/Form/SubscriptionSettingsForm.php
	src/Form/SubscriptionsBlockForm.php
	src/Form/SubscriptionsPageForm.php
	src/Plugin/Block/SimplenewsSubscriptionBlock.php
	src/Tests/SimplenewsSynchronizeFieldsFormTest.php