[Implement] EObject.EClass() method

[samatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the EcoreNetto
• I have searched open and closed issues to ensure it has not already been reported

Description

Implement the EObject.EClass() method such that it is possible to get access to the referenced EType of a StructuralFeature

e.g. to determine whther the EClass that a StructuralFeature has as a EType is abstract or not

Steps to Reproduce

System Configuration

• EcoreNetto: 2.3.1