Merge pull request #1562 from LLNL/features/db-locking

lib/spack/llnl/util/filesystem.py

lib/spack/llnl/util/lock.py

lib/spack/spack/cmd/debug.py

lib/spack/spack/cmd/diy.py

lib/spack/spack/cmd/install.py

lib/spack/spack/cmd/uninstall.py

lib/spack/spack/database.py

lib/spack/spack/file_cache.py

lib/spack/spack/package.py

lib/spack/spack/spec.py

lib/spack/spack/stage.py

lib/spack/spack/test/lock.py

lib/spack/spack/test/spec_dag.py

lib/spack/spack/util/crypto.py