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.
Fix the plugin add command not storing the resolved path for relative
paths passed to it into plugin-list.json and incorrectly resolving any
path containing ./ or ../ instead of only paths starting with these.
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.
Hornwitser