Detecting unused $dependencies

[jakub-g]

It would be interesting to have an option to remove dead dependencies, i.e. the deps that are defined in $dependencies but then not referenced anywhere in the code.

Right now those deps are already implicitly detected; the output of conversion looks like this:

var Aria = require("ariatemplates/Aria");
var modulesSthSth = require("modules/sth/Sth");
require("ariatemplates/utils/Data"); // this is not written to any variable -> it's actually an unused import
var ariaUtilsJson = require("ariatemplates/utils/Json");

To be decided if this should be the default behavior, probably yes, perhaps with a log to stderr about the fact.