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, …
In view_container.js, templateElement.parentNode can be null
when two template tags are nested in one another.
Accessing the parent node through view.nodes[0].parentNode fixes
the problem.
closes#997Closes#999