Implement new ValuesHKey

This is the next phase in the mapping between data and KV store. This removes the (most of) the dependency of HKey on the Persistit Key. This is done by implementing a new `ValuesHKey` which uses the `AbstractValuesHolderRow` as a storage for the data values. Meaning the HKey values are stored `Values` with the table ordinals stored separately. 

The `PersistitHKey` and `HKeyRow` classes have been deleted as unused, both replaced by the `ValuesHKey`. 

Most of the changes revolve around replacing `PersistitHKey` with `HKey` (the interface), and using the simplified interface. 

As  a separate step, I'll be getting rid of the `ValuesHKey` use of copyto/from `Key`. Also still broken is the `HKeyRow#ancestorHKey()`. While the class  is gone, the broken code has been moved into the new `ValuesHKey` class, and still needs to be fixed.