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/wget/package.py

@@ -0,0 +1,21 @@
+from spack import *
+
+class Wget(Package):
+    """GNU Wget is a free software package for retrieving files using
+       HTTP, HTTPS and FTP, the most widely-used Internet protocols. It
+       is a non-interactive commandline tool, so it may easily be called
+       from scripts, cron jobs, terminals without X-Windows support,
+       etc."""
+
+    homepage = "http://www.gnu.org/software/wget/"
+    url      = "http://ftp.gnu.org/gnu/wget/wget-1.16.tar.xz"
+
+    version('1.16', 'fe102975ab3a6c049777883f1bb9ad07')
+
+    depends_on("openssl")
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix,
+                  "--with-ssl=openssl")
+        make()
+        make("install")