mkrep.sh v2.3.0:
* Added '-f <From_ServerID>' flag to specify the ServerID from which
to replicate, a value used for the ReplicatingFrom: field.
* Added safety check to check that if '-t ha' is used with '-f',
the value for '-f' refers to an edge server.
* Added logic to replace the default value for ReplicatingFrom,
replacing naming-convention based logic with logic to dynamically
determine the value. This is done by finding the server spec with
Services of 'commit-server' or or 'standard', and using it. Or, if
that bares no fruit, doing 'p4 info' on the current server to extract
the ServerID.
* Enhancements to guidance info for creating edge servers and
filtered forwarding replicas, with details on using edge_dump.sh
or generating filtered replica checkpoints.
* Doc content and formatting improvements.
* Maintained shellcheck compliance.