Move LMDB into release version

[Arkatufus]

• Remove Akka.DistributedData.LightningDB beta status
• Add reference to Akka.DistributedData.LightningDB in Akka.Cluster.Sharding for easier end user implementation.

[Arkatufus]

Any user who needs to access LMDB from outside of Akka.Cluster.Sharding will still need to reference it manually, we can't include LMDB inside Akka.DistributedData unless we move the whole code into it (circular reference issue).
This is actually the case in scala Akka, LMDB is part of the Akka.DistributedData package, instead of its own standalone package.

[Aaronontheweb]

LGTM

[Aaronontheweb]

Any user who needs to access LMDB from outside of Akka.Cluster.Sharding will still need to reference it manually, we can't include LMDB inside Akka.DistributedData unless we move the whole code into it (circular reference issue).
This is actually the case in scala Akka, LMDB is part of the Akka.DistributedData package, instead of its own standalone package.

Should we just do that in a new release in the future? Pretty easy to deprecate packages on NuGet now.

[Arkatufus]

It should be trivial to do, Akka.DistributedData.LightningDB only contains 1 class file and 1 HOCON configuration file