checksums: use sha256 checksums everywhere

We'd like to use a consistent checksum scheme everywhere so that we can:

    a) incorporate archive checksums into our specs and have a
       consistent hashing algorithm across all specs.

    b) index mirrors with a consistent type of checksum, and not one that
       is dependent on how spack packages are written.

- [x] convert existing md5, sha224, sha512, sha1 checksums to sha256

var/spack/repos/builtin/packages/comd/package.py

@@ -23,7 +23,7 @@ class Comd(MakefilePackage):
     git      = "https://github.com/ECP-copa/CoMD.git"
 
     version('develop', branch='master')
-    version('1.1', '5051310a8d2c93cccba63de40bcfaa78')
+    version('1.1', sha256='4e85f86f043681a1ef72940fc24a4c71356a36afa45446f7cfe776abad6aa252')
 
     variant('mpi', default=True, description='Build with MPI support')
     variant('openmp', default=False, description='Build with OpenMP support')