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/memaxes/package.py

@@ -0,0 +1,19 @@
+from spack import *
+
+class Memaxes(Package):
+    """MemAxes is a visualizer for sampled memory trace data."""
+
+    homepage = "https://github.com/scalability-llnl/MemAxes"
+
+    version('0.5', '5874f3fda9fd2d313c0ff9684f915ab5',
+            url='https://github.com/scalability-llnl/MemAxes/archive/v0.5.tar.gz')
+
+    depends_on("cmake@2.8.9:")
+    depends_on("qt@5:")
+
+    def install(self, spec, prefix):
+        with working_dir('spack-build', create=True):
+            cmake('..', *std_cmake_args)
+            make()
+            make("install")
+