Adds the recommended kotlin-jpa compiler plugin for better support of JPA annotations in Kotlin.

It generates an additional zero-argument constructor for classes with a specific annotation.

This allows the Java Persistence API (JPA) to instantiate a class, although it doesn't have the zero-parameter constructor from Kotlin or Java point of view (see the description of kotlin-jpa plugin below).

Effectively, kotlin-jpa is wrapped on top of no-arg compiler plugin: The plugin specifies @Entity, @Embeddable, and @MappedSuperclass no-arg annotations automatically.