Cleanup templates www folder

We have a copy of the template that actually never gets used. It was being copied over by `create.js`, but wiped out when doing a `prepare`. It was then correctly replaced by the root project's `www` folder. See [the code here](https://github.com/apache/cordova-lib/blob/master/cordova-lib/src/cordova/metadata/firefoxos_parser.js#L151). The real template `www` is not platform specific and comes from https://github.com/apache/cordova-app-hello-world.

Copying of `cordova-lib` also happens during prepare. This is super confusing for platform developers and needs to go! :) @zalun, can you take a look?