Upgrade docker images to ubuntu 18.04

All images (except the openedx image, which requires ubuntu 16.04) are
upgraded.

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Changelog
 
+- 2018-11-28 [Improvement] Upgrade docker images to ubuntu 18.04 for android, forum, notes, xqueue
 - 2018-11-28 [Feature] Make it possible to define default platform language interactively
 - 2018-11-26 [Improvement] Make it easier to run a forked version of edx-platform
 - 2018-11-25 [Feature] Use local filesystem for open assessment file upload

android/Dockerfile

@@ -1,8 +1,8 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt update && \
   apt upgrade -y && \
-  apt install -y wget unzip git default-jre default-jdk
+  apt install -y wget unzip git openjdk-8-jre openjdk-8-jdk
 
 RUN mkdir /openedx
 

forum/Dockerfile

@@ -1,10 +1,10 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN mkdir /openedx
 
 RUN apt update && \
   apt upgrade -y && \
-  apt install -y git wget autoconf bison build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm3 libgdbm-dev
+  apt install -y git wget autoconf bison build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev
 
 # Install ruby-build for building specific version of ruby
 RUN git clone https://github.com/sstephenson/ruby-build.git /openedx/ruby-build

notes/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt update && \
   apt upgrade -y && \

xqueue/Dockerfile

@@ -1,8 +1,8 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt update && \
   apt upgrade -y && \
-  apt install -y language-pack-en git git-core python-pip libmysqlclient-dev
+  apt install -y language-pack-en git python-pip libmysqlclient-dev
 
 RUN mkdir /openedx
 RUN git clone https://github.com/edx/xqueue --branch open-release/hawthorn.2 --depth 1 /openedx/xqueue