Stringify `value` in ReactDOMInput / ChangeEventPlugin

This fixes two bugs related to string-casting in React:

 # Setting `<input value={0} />` would use an empty `value` because `0` is falsey.
 # Using `onChange` and `setState` with non-strings could lead to an infinite loop.

The latter is possible with controlled inputs when:

 - User changes input value.
 - `onpropertychange` fires.
 - `ChangeEventPlugin` dispatches `onChange`.
 - A handler responds via `this.setState` with a non-string value (e.g. a number).
 - The input re-renders and re-sets `value`.
 - The new `value` is not a string, but the current `value` (read from the element) is cast to a string automatically by the browser.
 - This triggers another `onpropertychange`.
 - `ChangeEventPlugin` dispatches another `onChange`.
 - ...
Cleanup console.* uses

* Stop doing `global.console && ...`
* Make sure all uses are behind `__DEV__` checks so they get stripped out
"use strict" for `ReactDoNotBindDeprecated`