Removed references to BlueGene/Q in core Spack

lib/spack/spack/architecture.py

lib/spack/spack/cmd/help.py

lib/spack/spack/operating_systems/cnk.py

lib/spack/spack/platforms/bgq.py

lib/spack/spack/test/architecture.py

lib/spack/spack/test/data/targets/bgq-rhel6-power7

lib/spack/spack/test/llnl/util/cpu.py