[eclipselink-dev] Check In - MappedKeyMapContainerPolicy

[Tom Ware <tom.ware@xxxxxxxxxx>]

https://bugs.eclipse.org/bugs/show_bug.cgi?id=241413

This patch passes the EclipseLink Core LRG, and the EclipseLink JPA LRG.
Additionally, it passes a set of CRUD tests implemented to test its
functionality.

This patch is for an initial check in that allows basic CRUD functionality to
work.

Included:
- Reading and writing of BasicMap, AggregateCollection, OneToMany,
UnidirectionalOneToMany, and ManyToMany map mappings with Direct, Aggregate or
Entity key fields through EclipseLink-proprietary API
- Converters on Direct Keys

Not done yet:
- Joining
- Batch Reading
- Private Ownership
- JPA Configuration
- new Expressions and JPQL

Will not do as part of this feature:
- History Policy
- Change Tracking