Adds pass_phrase property to the oracle-bmcs builder to allow users to
specify/override a pass phrase for the private key used to sign requests
to the BMCS API.
Implements a new Packer builder (oracle-bmcs) which adds support for
building custom images for Oracle Bare Metal Cloud Services (BMCS)
https://cloud.oracle.com/en_US/bare-metal.
Additionally includes documentation for the oracle-bmcs builder.