Support multiple php versions through vvv-config.yml & utilities

[LoreleiAurora]

This adds an additional optional variable of upstream to vvv-config.yml to allow you to set the nginx upstream.
It also switches xDebug from source to the PPA as this is compatible with multiple PHP versions.

An example config for testing:

---
sites:
  wordpress-default:
    repo: https://github.com/Varying-Vagrant-Vagrants/vvv-wordpress-default.git
    nginx_upstream: php71
    hosts:
      - local.wordpress.dev

  wordpress-develop:
    repo: https://github.com/Varying-Vagrant-Vagrants/vvv-wordpress-develop.git
    nginx_upstream: php56
    hosts:
      - src.wordpress-develop.dev
      - build.wordpress-develop.dev

  wordpress-trunk:
    repo: https://github.com/Varying-Vagrant-Vagrants/vvv-wordpress-trunk.git
    hosts:
      - local.wordpress-trunk.dev

utilities:
  core:
    - memcached-admin
    - opcache-status
    - phpmyadmin
    - webgrind
    - php56
    - php71

Requires Varying-Vagrant-Vagrants/vvv-utilities#3 to stop my custom repo being needed.

[jeremyfelt]

This is pretty slick! I left a couple comments inline. We should also update at least the wordpress-develop repository with the new nginx template variables, even if they end up being the default settings. This should help as a guide.

[jeremyfelt]

How about nginx_upstream or phpfpm_upstream? I doubt we'll ever use "upstream" elsewhere, but it may make it more clear.

[LoreleiAurora]

I decided on upstream instead of php_version as i realised it could be used for so much more than PHP, just as a test i have already run it with Node & Python upstreams.

[jeremyfelt]

Good point, using php here doesn't make sense.

I'm still going to be a pain. Let's do nginx_upstream. I think that clarifies the intent of the config. 😄

[jeremyfelt]

Looks like spacing may be off just a bit in these lines.

[LoreleiAurora]

Fixed, my IDE had used tabs instead of spaces 🙄

[jeremyfelt]

No reason to keep this waiting. I'll have time to do some more testing this weekend, but I'd like to get this in earlier than later. Thanks @LoreleiAurora!