HTML5/JS Apps: Add nodejs/npm/bower/grunt.. to the build server.

Most of the html5/js-webapps need nodejs and npm installed. I have little to no expereience if this somehow can be fixed with srclibs or from within our build recipes (in a sane way).

Recent app requesting for this was https://f-droid.org/forums/topic/eff-alerts/ .

On a side node, we might want to look into https://www.npmjs.com/package/license-checker to auto-restrict non-free packages, if we choose to install nodejs and npm.