Add check for pr.canRebase. This will be false if the PR has been modified.

Fixes #790

Previously, preset resolution was being done last, after merges of renoate.json or package.json config. This caused wrong ordering of config in cases where both presets + regular config was in use. Instead, resolving of presets is now done at each stage before merging.

Fixes #708

This PR implements eslint-inspired shareable configs. With this feature, we:
- Add new config option "extends"
  * This is an array of preset config names that the current config or preset extends/inherits from
- Add new config option "description"
  * Each preset config should include a description of its functionality that is human-readable
- Provide a set of commonly use configs called "preset defaults"
- Provide two "full" preset configs: "app" and "library"
   * Almost the same but app pins *all* version numbers while library only pins devdependencies
- Replace regular config in onboarding with one of these two presets
- Generate human-readable description of config in Onboarding PR
- Support npm for hosting configs (both scoped and non-scoped)

Closes #657, Closes #671, Closes #647 

* add massage test

* fix: return massaged config from migrateAndValidate

* fix: print schedule text along with error message

* update test

Also enables config errors to be shown in Configure Renovate PR.

Closes #550

Closes #637

It was a mistake to enable this feature by default, and should be disabled. A check has been made to set the status to “success” if it was previously “pending” and the setting is now false. This should also cover the case when someone enables it and then disables it.

Fixes #667

Updates definitions for schedule and package rules to allow strings to be massaged to lists - instead of erroring.

Closes #662

Fixes #656 

- Updated FAQ based on changes in #582
    - `packages` -> `packageRules`

Fixes #649