Adds platform support for Bitbucket cloud.

Closes #136, Closes #2238

Methods to support performing Git operation using filesystem instead of web API. GitHub only and experimental only. Usage: define env variable `RENOVATE_GIT_FS`.

Closes #1925

Contains GitHub specific changes from #2323

Related to #2323 and #1925

GitLab's API for closing issue is to send a PUT request with `state_event` set to `close`.

Reference: https://docs.gitlab.com/ce/api/issues.html#edit-issue

Fixes #2317

This reverts commit ba121836.

Converts to HTML then replaces hrefs to github.com with renovatebot.com/gh/. Skips if non-github.com endpoint detected.

Closes #1804

Pushes “getPrBody” logic into platform level to allow platforms to individually do things like text replacements and body length limiting.

Closes #2267

Retries every minute up to 5 times if receiving 429 from gitlab.

Closes #1578

Closes #2246

Delete cached issueList after creating any new issue, so that we don’t end up with “old” state and potentially create duplicate issues.

Adds option for useCache to github and gitlab wrappers.

This reverts commit 04e0ca1f.

Refactors credentials/token handling to rely less on env variables and instead use an endpoints middleware for credentials handling.

First step towards #2105

Closes #2200

Fixes call to Gitlab API.
Settings require direct path to API, the fixed string doubled it