The Node.js specific rules for Eslint were deprecated in favour of the
node plugin for Eslint. Add node plugin for eslint and switch over to
using its rules, fixing any issues detected.
Use relative imports in lib to avoid an issue with webpack thinking
absolute imports inside @clusterio/lib are for a separate module and
giving out warnings for it being missing in package.json.
Move the code for loading plugins infos from Node.js packages into a
separate module in order to break it out from lib/plugin.js which is
also used on the web interface side. This resolves a warning of using
an expression with require on the webpack build.
Hornwitser