Create default Dockerfile to be able to test basic scripts

Create a Dockerfile and add it to the repository to allow testing of EMADL models using the streamtest plugin.

Something like that would work (dependency is a local jdk-8u271-linux-x64.tar.gz file which is the Oracle JDK 8):

FROM ubuntu:bionic

RUN apt update && apt install -y --no-install-recommends maven g++ make cmake libarmadillo-dev

WORKDIR /root
COPY jdk-8u271-linux-x64.tar.gz .
RUN tar -xzf jdk-8u271-linux-x64.tar.gz
RUN rm jdk-8u271-linux-x64.tar.gz
RUN mv jdk1.8.0_271 /opt
RUN update-alternatives --install "/usr/bin/java" "java" "/opt/jdk1.8.0_271/bin/java" 1
RUN update-alternatives --set "java" "/opt/jdk1.8.0_271/bin/java"

A corresponding .gitlab-ci.yml would look like this (settings.xml and pom.xml files are mandatory):

stages:
  - integration

testIIR:
  stage: integration
  image: registry.git.rwth-aachen.de/se-student/ws2021/labs/connectedcars/ema
  script:
    - mvn streamtest:streamtest-execute -s settings.xml
  except:
    changes:
      - README.md
      - .gitignore
      - .gitkeep

In the mean time: Feel free to choose this image for testing of basic models (which do not have any specific dependencies)