feat: unify file locations

feat(bitbucket): Enable bitbucket reviewers

Document how to sign gitFs commits, remove the disabling of gpg signing.

Closes #3053, Closes #3472

Closes #2482 

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 #1262

Adds platform support for Bitbucket cloud.

Closes #136, Closes #2238

Added content as suggested/contributed by @swashata.

Closes https://github.com/renovatebot/config-help/issues/71

Closes #2168

Updates renovateapp -> renovatebot