add a scripts module __main__

makes (my) windows dev easier to execute without pip installing

planet/scripts/__init__.py

@@ -18,6 +18,3 @@
 assert v1  # appease lint
 
 main = cli.cli
-
-if __name__ == '__main__':
-    main()

planet/scripts/__main__.py

@@ -0,0 +1,4 @@
+from . import main
+
+if __name__ == '__main__':
+    main()