Add a default static route for each module

From https://discuss.tryton.org/t/how-to-create-grid-view-or-whoever-can-support-to-create-grid-view/2115/10

It may be simplify the developer life if we add such dynamic route that serves static content from a static folder. E.g. '/<module>/static/' that will serve the static directory inside the module.
We must just be careful to only serve content inside this directory (could reuse tools.file_open).