- 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
* r-matr: Create new package.
* shocklibs: Create new package.
* r-biom-utils: Create new package.
* r-mgraster: Create new package
* py-poster: Create new package.
* py-requests-toolbelt: Create new package.
* perl-libwww-perl: Create new package.
* py-mg-rast-tools: Create new package.
* mg-rast-tools: Fix version constraints for dependencies.
* Change dependency type of py-setuptools.
