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/uncrustify/package.py

@@ -0,0 +1,14 @@
+from spack import *
+
+class Uncrustify(Package):
+    """Source Code Beautifier for C, C++, C#, ObjectiveC, D, Java, Pawn and VALA"""
+
+    homepage = "http://uncrustify.sourceforge.net/"
+    url      = "http://downloads.sourceforge.net/project/uncrustify/uncrustify/uncrustify-0.61/uncrustify-0.61.tar.gz"
+
+    version('0.61', 'b6140106e74c64e831d0b1c4b6cf7727')
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix)
+        make()
+        make("install")