New, cleaner package repository structure.

Package repositories now look like this:

    top-level-dir/
        repo.yaml
        packages/
            libelf/
                package.py
            mpich/
                package.py
            ...

This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).

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

@@ -0,0 +1,20 @@
+from spack import *
+import os
+
+class Munge(Package):
+    """ MUNGE Uid 'N' Gid Emporium """
+    homepage = "https://code.google.com/p/munge/"
+    url      = "https://github.com/dun/munge/releases/download/munge-0.5.11/munge-0.5.11.tar.bz2"
+
+    version('0.5.11', 'bd8fca8d5f4c1fcbef1816482d49ee01', url='https://github.com/dun/munge/releases/download/munge-0.5.11/munge-0.5.11.tar.bz2')
+
+    depends_on('openssl')
+    depends_on('libgcrypt')
+
+    def install(self, spec, prefix):
+        os.makedirs(os.path.join(prefix, "lib/systemd/system"))
+        configure("--prefix=%s" % prefix)
+
+        make()
+        make("install")
+