Add the possibility to declare multiple scripts/stylesheets in gulp-paths.json

[nesk]

This would be especially useful for the IE8 polyfill, it would allow to move it to the vendor section, which applies less transformations than the app one :

{
    // ...

    "src": {
        "common": {
            "copy": ""
        },

        "vendor": {
            "stylesheets": {
                "vendor": "bower_components/normalize.css/normalize.css"
            },
            "scripts": {
                "ie8-support": [
                    "bower_components/html5shiv/dist/html5shiv.js",
                    "bower_components/es5-shim/es5-shim.js"
                ]
            }
        },

        "app": {
            "icons": {},

            "sprites": {},

            "stylesheets": {
                "app": "%theme_path%/app/stylesheets/*.less"
            },

            "scripts": {
                "app": "%theme_path%/app/scripts/app.js"
            }
        }
    },

    // ...
}