Propose to enable CSS source map generation while using the Oyejorge Less compiler in the Developer mode

https://github.com/magento/magento2/issues/2813

For now, you can generate source maps using Grunt: http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/css-topics/css_debug.html
But it will be useful to to it using the Oyejorge Less compiler.