use Grunt to build the dw-2.0[.min].js

This eliminates the need for a bash. Not sure if we should have this build script
in dw.js/ instead, cause it more or less looks like that directory contains a
self-contained node package, even though "dw.js" is not registred at npmjs.

As I plan to use Grunt for more things, I thought it would make sense to have one
build script for the whole datawrapper project instead.
use Grunt to run the Propel build script
refactored the script to generate the template cache for extracting the messages
Merge branch 'grunt' into reorganize

Conflicts:
	.gitignore
	db/build.bat
	dw.js/make
	scripts/gen_template_cache.php
	www/static/js/dw-2.0.js