build: use gulp-based packaging

This is a POC of the Gulp-native build that works _with_ noder and _without_ the need of pulling Grunt nor atpackager - the power of default gulp plugins :-)

Sending this PR as a POC to discuss as before merging I would like to discuss and we all agree with the approach I would extract the noder-sepcific part to a separate Gulp plugin.

@mlaval @divdavem WDYT?