Renovate will now attempt to decrypt with existing default padding, and if that fails then try with RSA_PKCS1_PADDING.

If an encrypted npmToken is found alongside an unencrypted npmrc in config, then the token will replace any `${NPM_TOKEN}` placeholder found, or be appended to the end of the file. This enables large npmrc files to be defined in config without needing to enrypt the entire thing.

Closes #1796

Closes #1764 

commit 7e15d3d488c927df2f11f728f35d493e2821477d
Author: Rhys Arkins <rhys@arkins.net>
Date:   Wed Jan 10 14:26:44 2018 +0100

    Revert "refactor: use _auth= when migrating npm tokens"

    This reverts commit 4a2fdd04.

* chore(deps): update dependency prettier to v1.9.0

* run prettier

Closes #1079

* chore(deps): update dependency prettier to v1.8.0

* reformat

Also clarify docs that encrypted config must be contained in renovate.json (i.e. not package.json).

* chore(deps): update dependency eslint-config-airbnb-base to v12.0.0

* fix lint

A new config object `encrypted` can be defined at any level and contain encrypted configuration strings. Initial use is for encrypting an npm token for use with the hosted renovate app.

Closes #650