Distinguish between state and config in properties

[rjcorwin]

Currently a there is a bit of confusion between state and config all mixed up in Polymer Properties. Attributes such as name, label, error-message, and others are configuration where as value, disabled, and hidden are state. Both state and configuration use the HTML Element attributes system, often the Polymer Properties system as a helper. This is confusing not only for knowing how to use the API of inputs, it also results in configuration such as label getting mixed up in the form responses because of the use of Element.getProps()/Element.setProps(props) will snatch/set anything listed in Polymer Properties. Not only do we not need label in the Form Response data, if that label is configured to something new in the HTML, when resuming a form the old label caught up in the Form Response will be applied to that input as if it was state. In some situations this is a feature not a bug, but most often an unexpected side affect.