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, …
Needed to change Renderer.mergeChildComponentProtoViews to not create
new ProtoViews to be able to deal with cyclic references.
This commit is part of using the new render layer in Angular.
Marc Laval
Tobias Bosch
Pawel Kozlowski