Move the definition and implementation of the config command to
lib/shared_comhmands.js, this removes the need for lib config to depend
on the fs module, which is not accessible in web build.
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.
Use lib* prefix for the modules impored from the lib package to help
distinguish them more from ordinary variables. Fix up the naming
convention for files to be consistently lowercase_underscore for
JavaScript files.
Add a separate plugin-list.json file for storing which plugins are
available and the path to pass to require in order to load it. This
allows plugins to be published and installed as npm packages. And also
replaces the old method of installing plugins by putting them in the
plugins folder.