refactor: docker layout

docker/python-3.7.dockerfile

@@ -0,0 +1,8 @@
+FROM python:3.7
+
+RUN apt-get update && apt-get install -y ffmpeg libsndfile1
+RUN pip install musdb museval
+RUN pip install spleeter==1.4.4
+RUN mkdir -p /model
+ENV MODEL_PATH /model
+ENTRYPOINT ["spleeter"]