Implements commands as extensions using stevedore; adds run and init command.

bonobo/commands/__init__.py

@@ -0,0 +1,22 @@
+import argparse
+
+from stevedore import ExtensionManager
+
+
+def entrypoint():
+    parser = argparse.ArgumentParser()
+
+    subparsers = parser.add_subparsers(dest='command')
+    subparsers.required = True
+
+    def register_extension(ext):
+        parser = subparsers.add_parser(ext.name)
+        command = ext.plugin(parser)
+        parser.set_defaults(command=command)
+
+    mgr = ExtensionManager(namespace='bonobo.commands', )
+    mgr.map(register_extension)
+
+    args = parser.parse_args().__dict__
+    command = args.pop('command')
+    command(**args)