Seperate requirements to run the bot and to develop.

- Add a requirements-dev.txt file which includes additional deps for development.
- Add a Dockerfile.develop which installs all deps for development and also enables dev commands.
- Change related documentations on how to run/dev the bot.

Dockerfile.develop

@@ -0,0 +1,9 @@
+FROM freqtrade:latest
+
+# Install dependencies
+COPY requirements-dev.txt /freqtrade/
+RUN pip install numpy --no-cache-dir \
+  && pip install -r requirements-dev.txt --no-cache-dir
+
+# Empty the ENTRYPOINT to allow all commands
+ENTRYPOINT []