Issue #2002134 by fago, yched, amateescu, effulgentsia: Move TypedData metadata introspection from data objects to definition objects.

Issue #2047229 by fago, smiletrl, Berdir, effulgentsia, amateescu: Make use of classes for entity field and data definitions.

Issue #1614186 by RobLoach, tim.plunkett, msonnabaum, Crell, jhodgdon, Niklas Fiekas: Update coding standards for using 'native' PHP classes like stdClass in namespaced code.

Issue #1868004 by fago, das-peter, Berdir, EclipseGc, fubhy the cat, dixon_: Improve the TypedData API usage of EntityNG.

Issue #1877632 by fago, jhodgdon: Improve comments and clean-up code for EntityNG and the TypedData API.

Issue #1869250 by fago, Berdir, das-peter, YesCT, mradcliffe, fubhy: Various EntityNG and TypedData API improvements.

Issue #1696640 by fago, effulgentsia, tim.plunkett, dixon_, plach: Add a uniform Entity Property API.