Add travis ci, linter, merge shellcheck, fix some issues (#241)

* Quote all vars, remove useless echo/sub-shell, add shebands, fail on unset vars, enable pipefail, formatting

* Add CI including linting via hadolint nad shellcheck

* Update all base images to tag 3.9

* Switch to maintainer labels

* Quote vars

* Remove commented code

* Ignore if the folder exists

0.14/Dockerfile

@@ -1,11 +1,11 @@
-FROM frolvlad/alpine-glibc:alpine-3.4
+FROM frolvlad/alpine-glibc:alpine-3.9
 
-MAINTAINER https://github.com/dtandersen/docker_factorio_server
+LABEL maintainer="https://github.com/dtandersen/docker_factorio_server"
 
 ENV VERSION=0.14.23 \
     SHA1=6ef84341c6fc1cf45cfdd6acc8468aaa117b9e8a
 
-RUN mkdir /opt && \
+RUN mkdir -p /opt && \
     apk --no-cache add curl tini pwgen && \
     curl -sSL https://www.factorio.com/get-download/$VERSION/headless/linux64 \
         -o /tmp/factorio_headless_x64_$VERSION.tar.gz && \

0.14/docker-entrypoint.sh

@@ -30,6 +30,6 @@ fi
 exec /opt/factorio/bin/x64/factorio \
   --port 34197 \
   --start-server-load-latest \
-  --server-settings $CONFIG/server-settings.json \
+  --server-settings "$CONFIG/server-settings.json" \
   --rcon-port 27015 \
   --rcon-password "$(cat "$CONFIG/rconpw")"