refactor(render): use render layer fully

Introduces angular2/src/core/compiler/ViewFactory which
extracts ProtoView.instantiate and replaces ViewPool.

Note: This is a work in progress commit to unblock other commits.
There will be follow ups to add unit tests, remove TODOs, …

test-main.dart

@@ -1,11 +1,9 @@
 import 'package:guinness/guinness.dart';
 import 'package:unittest/unittest.dart' as unit;
-import 'package:angular2/src/dom/browser_adapter.dart';
 
 import 'package:angular2/src/test_lib/test_lib.dart' show testSetup;
 
 main() {
-  BrowserDomAdapter.makeCurrent();
   unit.filterStacks = true;
   unit.formatStacks = false;
   unit.unittestConfiguration.timeout = new Duration(milliseconds: 100);