Issue #2030633 by hussainweb, Mile23, carsonevans, czigor, Berdir, fernando_calsa, Geijutsuka, amitgoyal, Jānis Bebrītis, undertext: Expand FieldStorageConfig with methods

Issue #2164601 by yched, jibran, amateescu, pfrenssen: Stop auto-creating FieldItems on mere reading of $entity->field[N]

Issue #2232477 by plach, yched, tstoeckler, amateescu: Fatal when adding new fields with NOT NULL constraints in a base table that contains existing entities

Issue #2395395 by alexpott, effulgentsia, Gábor Hojtsy: TestBase lacks a config method to be used consistently in tests

Issue #2183983 by Gábor Hojtsy, vijaycs85, Berdir, Wim Leers, webflo, alexpott: Find hidden configuration schema issues

Issue #2384167 by tibbsa: Clean-up DateTime module test members — ensure property definition and use of camelCase naming convention

Issue #2370305 by Gábor Hojtsy, yched: Refactor field type configuration schemas for DX, easier to find errors

Issue #2378055 by Gábor Hojtsy: Reorganise config schema for entity_form_display / entity_view_display

Issue #2368349 by Gábor Hojtsy, alexpott: Entity view and form display configuration schemas are too verbose / key ones missing

Issue #2346911 by larowlan, vijaycs85, Berdir | sihv: Fixed Base field overrides have incorrect default value callable properties.

Issue #2343651 by xjm, tim.plunkett, Wim Leers, dinarcon, dawehner: Remove most remaining l() calls.

Issue #2312093 by alexpott, yched, andypost, swentel | xjm: Rename FieldInstanceConfig to FieldConfig.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.

Issue #2327363 by yched, andypost: Move datetime_datetime_widget_validate() to DateTimeDefaultWidget::massageFormValues().

Issue #2320157 by moshe weitzman, Wim Leers, penyaskito, tim.plunkett: Generate placeholder content for Field types.

This reverts commit 3ac426f9.

Issue #2226493 by Berdir, Wim Leers, m1r1k, mr.baileys, andypost, scor, cbr, joelpittet: Apply formatters and widgets to Node base fields.

Issue #2088365 by Cottser, CharuAg, bradklaver, machostache, cs_shadow, visabhishek, sriharsha.uppuluri, grisendo, undertext, naveenvalecha | nod_: Fixed Wrong name for datetime.html.twig should be time.html.twig.

Issue #1976158 by Berdir | msonnabaum: Rename entity storage/list/form/render "controllers" to handlers.

Issue #2306539 by swentel, alexpott, sun: Fixed FieldUnitTestBase::createFieldWithInstance() pollutes test class with arbitrary properties.

Issue #2149197 by penyaskito, mikey_p, vijaycs85, herom: Replace format_interval with \Drupal::service('date')->formatInterval().