* Bugfix/Installer: properly track task queueing
* Move ordinal() to llnl.string; change time to attempt
* Convert BuildTask to use kwargs (after pkg); convert STATUS_ to BuildStats enum
* BuildTask: instantiate with keyword only args after the request
* Installer: build request is required for initializing task
* Installer: only the initial BuildTask cannnot have status REMOVED
* Change queueing check
* ordinal(): simplify suffix determination [tgamblin]
* BuildStatus: ADDED -> QUEUED [becker33]
* BuildTask: clarify TypeError for 'installed' argument
Modifications:
- [x] Move `spack.util.string` to `llnl.string`
- [x] Remove dependency of `llnl` on `spack.error`
- [x] Move path of `spack.util.path` to `llnl.path`
- [x] Move `spack.util.environment.get_host_*` to `spack.spec`