Update installed packages

* remove git, which was not used
* use the base image for building, which saves us installing one or two things
* add a bunch of stuff so that the images build for arm/v7

extras/docker/base/Dockerfile

@@ -16,15 +16,12 @@ LABEL maintainer="Roland Geider <roland@geider.net>"
 ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get update \
   && apt-get install --no-install-recommends -y \
-      git \
       locales \
       nodejs \
       npm \
-      python3-venv \
       python3-pip \
       sqlite3 \
       wget \
-      libpq5 \
   && rm -rf /var/lib/apt/lists/* \
   && npm install -g yarn sass\
   && locale-gen en_US.UTF-8