[WIP] Upgrade to Xenial

[auxesis]

Morph currently runs on Ubuntu 12.04 Precise. Precise reached end of life on April 28, 2017.

This PR is an experiment in building a Xenial-based image with Packer, to run Morph on.

The current intention is to:

• Build a new server for Morph to run on
• Deploy the Morph app to the new server
• Migrate data from the existing server to the new server
• Point DNS from the old server to the new
• Turn off the old server

[auxesis]

Current status:

• Switched to installing RVM through packages (acba954)
• Investigated switching to a PPA to install Redis, but decided to make source-based install + config work on Xenial, and optimise the build (ac00d46 a866d3d 3f0e56d d55ae6c)
• Removed newrelic-sysmond because New Relic are deprecating it in favour of New Relic Infrastructure (e7fc16a)
  • Removed build of Discourse, as I consider it to be outside the scope of this spike, and I've already spiked splitting it out entirely. (722aec7)

Next:

• [ ] Make secrets + credential management work (the Ansible role for mitmdump is failing because it doesn't have secrets).
• [ ] Commit the make based process for building images with Packer + Ansible.
• [ ] Modify the Travis config to be a build matrix for apps + images. Always build + test app changes, but bail the image build if there are no changes under provisioning/.
• [ ] Experiment with writing a simpler Python script for generating Ansible inventory from Digital Ocean. There's an existing one but it doesn't cache properly, and doesn't handle emitting images and droplets at the same time.
• [ ] Experiment with adapting the Python script to output a variable make can use to dynamically generate the inventory, so we can run Ansible against an image we're developing, or a PR that's been built.

/cc @henare @equivalentideas

[mlandauer]

@auxesis I'm sorry I didn't know about this before I started working on the same thing which is now merged into master and deployed on the new server.

I'm not familiar with Packer. Do you think that's still a good thing to do?

In the meantime, I'll close this PR.