Started work on cli, which also meant adding setup.py

I'm using click, and click recommends using a setup.py - so I've added one of
those. I also refactored code into a new datasite package. It's not quite
deploying to now properly at the moment though - I seem to have messed up the
path handling a bit.

Also snuck in a new template for the "Row" view.

Refs #40

Dockerfile

@@ -1,7 +1,7 @@
 FROM python:3
 COPY . /app
 WORKDIR /app
-RUN pip install -r requirements.txt
-RUN python app.py --build
+RUN pip install .
+RUN datasite build
 EXPOSE 8006
-CMD ["python", "app.py"]
+CMD ["datasite", "serve", "--port", "8006"]