Create a python script for rewriting in-place layers.

Using in-place layers makes it impossible to see the state of an
individual layer, so this script rewrites them into each having their
own output layer.

tools/Makefile

@@ -0,0 +1,7 @@
+MKDIR=mkdir -p
+
+all: generated
+
+generated: $(wildcard proto/*.proto)
+	$(MKDIR) $@
+	protoc --python_out="$@" $^