cmd/projector accepts `vbuckets` cmdline switch.
cmd/projector accepts `vbuckets` cmdline switch.

This is similar to cmd/indexer that accepts the maximum number of
vbuckets configured in the cluster.

Change-Id: Id4c5b441e5738a2a685bb03ea4fa98a5f8315fc6

jchris/indexing,jchris/indexing,jchris/indexing,jchris/indexing