Update base image to Ubuntu 18.04 (#862)

* Moved Dockerfiles to build for ubuntu 18.04

* Moved gnupg2 from NodeBase to Base image

* Updated base image to even newer bionic beaver version

Author: ThomasMeschke

Base/Dockerfile

@@ -1,12 +1,12 @@
-FROM ubuntu:xenial-20181113
+FROM ubuntu:bionic-20181204
 LABEL authors="Selenium <selenium-developers@googlegroups.com>"
 
 #================================================
 # Customize sources for apt-get
 #================================================
-RUN  echo "deb http://archive.ubuntu.com/ubuntu xenial main universe\n" > /etc/apt/sources.list \
-  && echo "deb http://archive.ubuntu.com/ubuntu xenial-updates main universe\n" >> /etc/apt/sources.list \
-  && echo "deb http://security.ubuntu.com/ubuntu xenial-security main universe\n" >> /etc/apt/sources.list
+RUN  echo "deb http://archive.ubuntu.com/ubuntu bionic main universe\n" > /etc/apt/sources.list \
+  && echo "deb http://archive.ubuntu.com/ubuntu bionic-updates main universe\n" >> /etc/apt/sources.list \
+  && echo "deb http://security.ubuntu.com/ubuntu bionic-security main universe\n" >> /etc/apt/sources.list
 
 # No interactive frontend during docker build
 ENV DEBIAN_FRONTEND=noninteractive \
@@ -28,6 +28,7 @@ RUN apt-get -qqy update \
     jq \
     curl \
     supervisor \
+    gnupg2 \
   && rm -rf /var/lib/apt/lists/* /var/cache/apt/* \
   && sed -i 's/securerandom\.source=file:\/dev\/random/securerandom\.source=file:\/dev\/urandom/' ./usr/lib/jvm/java-8-openjdk-amd64/jre/lib/security/java.security