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/py-illumina-utils/package.py

@@ -13,8 +13,8 @@ class PyIlluminaUtils(PythonPackage):
     homepage = "https://github.com/meren/illumina-utils"
     url      = "https://pypi.io/packages/source/i/illumina-utils/illumina-utils-2.2.tar.gz"
 
-    version('2.3', 'c0af71723e52ab2b14660d2138620e39')
-    version('2.2', '9e19cf112ccc38a903fc41f431804d21')
+    version('2.3', sha256='0e8407b91d530d9a53d8ec3c83e60f25e7f8f80d06ce17b8e4f57a02d3262441')
+    version('2.2', sha256='6039c72d077c101710fe4fdbfeaa30caa1c3c2c84ffa6295456927d82def8e6d')
 
     depends_on('python@3:', type=('build', 'run'))
     depends_on('py-pip', type='build')