Initial setup

The point of this is to separate dockerfiles and build them on top of
each other wherever possible.

Then we can build them interdependently with makefiles!

openwrt-builder-commit.dockerfile

@@ -0,0 +1,9 @@
+FROM openwrt-builder
+
+ARG commit
+
+RUN git pull origin master
+
+RUN git checkout ${commit}
+
+