Add DOCKERFILE

This adds a docker setup as in #1 to run the examples and some hints in the readme on how to use it.

It uses the "isolated" way to run GUI in docker containers described in http://wiki.ros.org/docker/Tutorials/GUI#The_isolated_way . I think it should be sufficiently secure. The only downside is that you have to change the DOCKERFILE if your user is not the primary user on your system.

Dockerfile

+FROM osrf/ros:melodic-desktop-full-bionic
+
+ARG uid=1000
+ARG gid=1000
+
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+ENV USERNAME ros
+RUN useradd -m $USERNAME && \
+        echo "$USERNAME:$USERNAME" | chpasswd && \
+        usermod --shell /bin/bash $USERNAME && \
+        usermod -aG sudo $USERNAME && \
+        echo "$USERNAME ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers.d/$USERNAME && \
+        chmod 0440 /etc/sudoers.d/$USERNAME && \
+        # Replace 1000 with your user/group id
+        usermod  --uid $uid $USERNAME && \
+        groupmod --gid $gid $USERNAME
+
+RUN apt-get update && apt-get install -y \
+      python-catkin-tools bash
+WORKDIR /home/$USERNAME
+COPY src /home/$USERNAME/src
+RUN rosdep install --from-paths . -r -y
+RUN catkin config \
+      --extend /opt/ros/melodic && \
+    catkin build
+
+ENTRYPOINT ["/entrypoint.sh"]