Issue #2453175 by tim.plunkett, plach, rteijeiro, effulgentsia, eshta, dawehner, fago, Berdir, alexpott: Remove EntityFormInterface::validate() and stop using button-level validation by default in entity forms

Revert "Issue #2459753 follow-up by tim.plunkett, alexpott: EntityForm::validate() should be able to modify the form structure"

This reverts commit fb5ea78b.

Issue #2459753 follow-up by tim.plunkett, alexpott: EntityForm::validate() should be able to modify the form structure

Revert "Issue #2459753 by tim.plunkett: EntityForm::validate() should be able to modify the form structure"

This reverts commit d4d83576.

Issue #2392319 by alexpott, effulgentsia: Config objects (but not config entities) should by default be immutable

Issue #2345793 by tim.plunkett | xjm: Entities should provide a method for a properly generated link to the entity.

Issue #1182850 by xjm, Stefan Lehmann, jmcintyre, Bojhan: Remove full stops at the end of checkbox options.

Issue #2030591 by jibran, Temoor, andypost, lokeoke, er.pushpinderrana, martin107, pcambra, piyuesh23, Sharique, kgoel | plopesc: Expand ContactForm with methods.

Issue #2308821 by tim.plunkett: Replace FormErrorInterface with $form_state->setErrorByName() and $form_state->setError().

Issue #2272481 by herom, ParisLiakos, tim.plunkett: Remove usages of watchdog() from forms, plugins and controllers.

Issue #2072897 by jayeshanandani, marcingy, herom, er.pushpinderrana, inket: Modernize contact.module forms.

Issue #2115631 by andypost, socketwench: Fixed CategoryFormController::form() should not define form actions.

Issue #950534 by mparker17, mgifford, Mixologic, jbloomfield, erinclerico, theMusician, wmostrey | zirvap: [policy] Consistently use email instead of e-mail in Drupal.

Issue #2190313 by pfrenssen, Berdir, amateescu, ianthomas_uk: Add $EntityType::load() and loadMultiple() to simplify loading entities.

Issue #2145007 by tim.plunkett, h3rj4n: Convert form_set_error() in FormBase classes to use FormErrorInterface.

Issue #1856556 by Berdir, andypost, das-peter: Convert user contact form into a contact category/bundle.

Issue #1913618 by tim.plunkett, amateescu: Convert EntityFormControllerInterface to extend FormInterface.

Issue #1588422 by andypost, sun, disasm, dawehner, vasi1186, alexpott, tim.plunkett, larowlan: Convert contact categories to configuration system.

Issue #1588422 by andypost, disasm, sun, dawehner, vasi1186, alexpott, tim.plunkett, larowlan, Gábor Hojtsy: Convert contact categories to configuration system.