Redesigns Renovate’s Dockerfile to use Ubuntu 18 as its base.

Closes #3063

BREAKING CHANGE: Renovate now requires Node.js 10.x to run

Rename all VSTS references to be Azure DevOps.

Closes #2810

BREAKING CHANGE: 'vsts' platform is now renamed to 'azure'

Deprecate use of “special” env var like `GITHUB_TOKEN` and instead standardize on `RENOVATE_*` environment variables instead.

Closes #2834

BREAKING CHANGE: For GitHub, GitLab, Bitbucket and VSTS you need to migrate `*_ENDPOINT` to `RENOVATE_ENDPOINT`, `*_TOKEN` to `RENOVATE_TOKEN`, and same for `BITBUCKET_USERNAME` and `BITBUCKET_PASSWORD`.

I haven’t used Heroku with Renovate in over a year and am not able to directly support it. I think it would be best to be made into a “wrapper” repository like https://github.com/renovatebot/renovate-heroku

BREAKING CHANGE: renovate repository no longer supports direct deployment to Heroku

Closes #3096

Catches an edge case where a PR is configured for automerge and a new update comes right before automerge. If branch protection wasn’t configured, Renovate was using a “stale” branch status to think it’s OK to merge. Added an additional check before automerging that should catch it.

Fixes #3099

Closes #3088

This reverts commit 625fa474.

Needed for package managers that support more than one depType (e.g. Bundler).

Closes #3076

Closes #3078

Closes #3082

Closes #3072