Reorganize files

This is just moving a bunch of DOM files.

It moves things into dom/stack and dom/fiber respectively. The
dom/stack folder remains split into client/server.

Mainly the shared folder is now my best guess for files that
we can reuse in fiber. Everything else will get forked or
reimplemented.

Also moved the event system out of renderers/shared/stack and
into renderers/shared/shared.

src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js

@@ -628,7 +628,7 @@ describe('ReactDOMComponent', () => {
     beforeEach(() => {
       var ReactDOMInjection = require('ReactDOMInjection');
       ReactDOMInjection.inject();
-      var ReactDOMStackInjection = require('ReactDOMInjection');
+      var ReactDOMStackInjection = require('ReactDOMStackInjection');
       ReactDOMStackInjection.inject();
 
       var ReactDOMComponent = require('ReactDOMComponent');