Created a VS Code Container configuration for the WorkDir project.

The idea is that for VS Code based development we should rely on
the container capabilities of the editor. Letting it create a terminal
for us that we could compile code in, while relying on the files
and environment created inside the container, to interpret our code.

.devcontainer/Dockerfile

+# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+
+# Start from the base CERN CentOS 7 image.
+FROM cern/cc7-base:latest
+
+# Perform the image setup as root.
+USER root
+WORKDIR /root
+
+# Install some additional packages.
+RUN yum -y install which git wget tar atlas-devel libuuid-devel texinfo       \
+           redhat-lsb-core libX11-devel libXpm-devel libXft-devel             \
+           libXext-devel openssl-devel glibc-devel rpm-build libcurl-devel && \
+    yum clean all
+
+# Set up the ATLAS user, and give it super user rights.
+RUN echo '%wheel	ALL=(ALL)	NOPASSWD: ALL' >> /etc/sudoers && \
+    adduser atlas && chmod 755 /home/atlas && \
+    usermod -aG wheel atlas
+
+# Copy the interactive environment setup scripts in place.
+COPY atlas_prompt.sh setup_atlas.sh /etc/profile.d/
+# Add the message of the day instructions for the image.
+COPY motd /etc/
+
+# Switch to the ATLAS account.
+USER atlas
+WORKDIR /home/atlas
+
+# Set up the command to run when starting the image.
+CMD cat /etc/motd && /bin/bash

.devcontainer/atlas_prompt.sh

+# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+#
+# Tweaks to the prompt seen by the user in interactive mode.
+#
+
+# Set up a nice prompt:
+export PS1='\[\033[01;35m\][bash]\[\033[01;31m\][\u]\[\033[01;34m\]:\W >\[\033[00m\] ';
+
+# Enable color output for the terminal:
+export CLICOLOR=1

.devcontainer/devcontainer.json

+{
+    "name": "CentOS 7",
+    "dockerFile": "Dockerfile",
+
+    "runArgs": [
+        "-v", "/cvmfs/atlas.cern.ch:/cvmfs/atlas.cern.ch:cached",
+        "-v", "/cvmfs/atlas-nightlies.cern.ch:/cvmfs/atlas-nightlies.cern.ch:cached",
+        "-v", "/cvmfs/atlas-condb.cern.ch:/cvmfs/atlas-condb.cern.ch:cached",
+        "-v", "/cvmfs/sft.cern.ch:/cvmfs/sft.cern.ch:cached",
+        "-v", "${localWorkspaceFolder}/../build:/workspaces/build:delegated"
+    ],
+
+    "settings": {
+        "terminal.integrated.shell.linux": "/bin/bash"
+    },
+
+    "extensions": [
+        "ms-vscode.cpptools",
+        "twxs.cmake"
+    ]
+}

.devcontainer/motd

+                _ _____ _      _   ___ 
+               /_\_   _| |    /_\ / __|
+              / _ \| | | |__ / _ \\__ \
+             /_/ \_\_| |____/_/ \_\___/
+
+This is the ATLAS VS Code development image. To set up
+your build, set up your build environment as usual (using
+setupATLAS and asetup), and then set up your build like:
+
+cmake -DATLAS_PACKAGE_FILTER_FILE=some_filter_file.txt \
+   /workspace/athena/Projects/WorkDir/
+

.devcontainer/setup_atlas.sh

+# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+#
+# Add the setupATLAS command, as a BASH function, to the environment.
+#
+
+setupATLAS() {
+    export ATLAS_LOCAL_ROOT_BASE=/cvmfs/atlas.cern.ch/repo/ATLASLocalRootBase
+    source $ATLAS_LOCAL_ROOT_BASE/user/atlasLocalSetup.sh
+}

.vscode/c_cpp_properties.json

@@ -9,7 +9,7 @@
             "compilerPath": "${env:CXX}",
             "cStandard": "c11",
             "cppStandard": "c++17",
-            "intelliSenseMode": "clang-x64",
+            "intelliSenseMode": "gcc-x64",
             "compileCommands": "${workspaceFolder}/../build/compile_commands.json"
         }
     ],