Started on form test for field sync
Merge branch '8.x-1.x' into personalization
Fixed failing sync form test
Made SubscriptionsAccountForm extend ContentEntityForm
Extracted SubscriberFormBase from SubscriptionsAccountForm and SubscriberForm
Let SubscriberAccountForm create new Subscriber with same email.
Made SubscriptionsBlockForm extend SubscriberFormBase
Merge branch '8.x-1.x' into personalization
Enabled subscriptions widget, refactored BlockForm, call Subscriber::un/subscribe() on submit
Controlling un/subscribe() calls based on available options
Updated testSubscribeAnonymous() and fixed some detected implementation flaws.
Made SubscriptionsPageForm extend SubscriberFormBase
Refactored form submit into separate callbacks
Considering the sync settings option
Reset subscriptions field after copyValuesToEntity()
Fixes, greener SubscribeTest
Fixes regarding order of submit actions
Avoid duplicate email
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
Merge branch '8.x-1.x' into personalization