* Add options for hashes, tree depth, and YAML to `spack spec`.
- Can now display hashes with `spack spec`, like `spack find`.
- Removed the old "ids" argument to `spack spec` (which
printed numerical values)b
- Can output YAML spec from `spack spec` with `-y`
- Can control depth of DAG traversal with --cover=[nodes|edges|paths]
- Can print install status (installed, missing, not installed) with -I
* Don't use YAML aliases in specs.
- Force Spack's YAML dumper to ignore aliases.
- aliases cause non-canonical YAML to be used in DAG hash, and result in
redundant hashes.
- add a test to ensure this behavior stays
2536029ea9