* add version 7.0.1
* replace md5 with sha256 for various versions.
* v7.0.1 fixes some environment hacking to properly find MPI and
system architecture
- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
