Add Replication Network feature documentation

Replication network support was added to 1.9.0 release of
Swift. This update includes instructions how to configure
this feature and description of how it generally works.
More specific information on the replication network was
added to Swift Developer documentation.

bug #1123067

Change-Id: I1cebec7c105690e9be72f314fc3aaecdfaf2e3f9
Merge "Add Replication Network feature documentation"