- Added a new interface for Specs to pass build information
- Calls forwarded from Spec to Package are now explicit
- Added descriptor within Spec to manage forwarding
- Added state in Spec to maintain query information
- Modified a few packages (the one involved in spack install pexsi) to showcase changes
- This uses an object wrapper to `spec` to implement the `libs` sub-calls.
- wrapper is returned from `__getitem__` only if spec is concrete
- allows packagers to access build information easily
