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/wxpropgrid/package.py

@@ -0,0 +1,20 @@
+from spack import *
+
+class Wxpropgrid(Package):
+    """wxPropertyGrid is a property sheet control for wxWidgets. In
+       other words, it is a specialized two-column grid for editing
+       properties such as strings, numbers, flagsets, string arrays,
+       and colours."""
+    homepage = "http://wxpropgrid.sourceforge.net/"
+    url      = "http://prdownloads.sourceforge.net/wxpropgrid/wxpropgrid-1.4.15-src.tar.gz"
+
+    version('1.4.15', 'f44b5cd6fd60718bacfabbf7994f1e93')
+
+    depends_on("wx")
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix, "--with-wxdir=%s" % spec['wx'].prefix.bin, "--enable-unicode")
+
+        make()
+        make("install")
+