generically treat data/main.js for views/app.js usage

react-main.js may not need to be touched for most uses. data/main will
change, and views/app will see a representative Cortex object in
`this.props.data`. New projects can probably leave index.html and
react-main.js alone.
stub in router with inane example.

again, react-main may never need to be touched. router has static
variables for all routes, and components can use adhoc routing.