Add support to CQL and NTS for configuring keyspaces to have transient replicas.
Add syntax allowing a keyspace using NTS to declare some replicas in each DC as transient.
Implement metadata internal to the DB so that it's possible to identify what replicas are transient for a given token or range.
Introduce Replica which is an InetAddressAndPort and a boolean indicating whether the replica is transient. ReplicatedRange which is a wrapper around a Range that indicates if the range is transient.
Block altering of keyspaces to use transient replication if they already contain MVs or 2i.
Block the creation of MV or 2i in keyspaces using transient replication.
Block the creation/alteration of keyspaces using transient replication if the experimental flag is not set.
Update web site, CQL spec, and any other documentation for the new syntax.