["bug"] Improve Dockerfile layer caching

[ecsmyth]

Description:

The current order of steps in the Dockerfile has some expensive infrequent tasks (e.g., pip install -q .) occurring after more frequently modified file are copied (e.g., src). The breaks layer caching and causes image builds to take longer than necessary.

Steps to reproduce:

1. Run ./script/server
2. Modify a file in ./src
3. Run ./script/update

Expected behavior:

The step RUN pip install -q . is cached

What I got instead:

The step RUN pip install -q . needs to execute