Feature: Add devops-init and devops-build.

## Ready State: No

Adds two drush_devops commands: devops-init and devops-build.

### devops-init

Sets up folder structure for having a vhost/site directory, a
builds directory for the destination of the result of individual
builds, and a headless repo for storing the results of the builds.

### devops-build

Adds command to download a make file, run a full build of the site
from the make file, commit the result of the build and push it to
the headless buildsrepo, and deploy the new build code to the
site/vhost.

## Requirements & Dependencies

* None

## Deployment Instructions

* Merge code, install utility in your environment.
* Clear drush caches with `drush cache-clear drush`

## Usage/Test Instructions

* Run `drush devops-init` from an empty directory nested inside another empty directory, or pass it the path of an existing empty directory or the name of a directory you'd like it to create to house your site/vhost `drush devops-init my-site`.
* Check to see that three directories exist, the vhost/site, the build destination, and the builds repo. The vhost/site and build destination should both contain .git directory and a .gitigore file and should currently have the 7.x-1.x-builds branch checked out. The builds repo directory should contain a headless repo.
* Run `drush devops-build build-my-site.make` passing in the path to the build file you're building from (can be local file or publicly accessible remote path). Alternatively, run the command with the name of your build file and github details to download the file from a github repo `drush devops-build build-my-site.make --github_user=my-github-username --github_project=my-github-repo-name --github_token=my-github-access-token --github_ref=7.x-1.x`
* Check to see that the build succeeded to run without error and that the site/vhost now contains a fully file populated site. The repo should be checked out to the 7.x-1.x-builds branch and the git log should now show 2 commits in it, the initial commit and a build commit containing the result of the build you just ran.