unbreak server-side/web worker

We're now trying to access document directly at require time. Wrapping in a function prevented that before. But we can simply check what environment we're in first.
dom-property-config: move constants to own file

This prepares the DefaultDOMPropertyConfig.js file to be broken
  out by breaing it's tight coupling to DOMProperty.js

This will reduce complexity and size of `dom-property-config`
  module
export Constants used in this file

This will allow users of this module to understand what the
  flags mean without needing to know about the flags file
dom-property-config Set header in new file

Must set the correct header including the providesModule
  directive
dom-property-config: Package description for dom-property-config

Written a README.md & package.json for the new module
dom-property-config: Add a grunt target to build module

Added a grunt target to build the dom-property-config module.
document how to contribute