Setup and Configure Nexus

Setup and Configure Nexus

Adds the Nexus (v2) container and does the following:

 - Creates the initial 'logs' repository
 - Configures Jenkins to be able to talk to Nexus by creating a
   settings.xml, and installing the needed packages on the
   jenkins-agent.
 - Installs required plugins for the jjb logs publishing job, including
   downloading PostBuildScript during the Jenkins container build.
 - Directs requests to 'jenkins.localhost', etc, on the jenkins-agent
   through the nginx container.
 - Sets the Jenkins Markup Formatter to 'Safe HTML' so the logs link can
   be displayed.

Change-Id: I63c783156bcffd1699e9ca7fe1a114ee2ed54bed
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>