move shared files up to superclass

Addresses issue https://github.com/sethladd/stagehand/issues/20
We'd need things like:

- a js web app
- JS and dart chrome apps
- a node.js server example

in addition to the dart ones that stagehand will also have. The gitignore files for some of those app types will be different. And, CDE may find it useful to use generators to create fragments of applications in addition to full apps. So, think a new JS polymer element.

I'm just assuming a lot of that is out of scope for stagehand. Totally agree with the idea of minimizing flexibility - it does not help a project to try and be all things to all people.