Separate page model from page actions

As part of converting the Channel Manager to Angular the second step is to sanitize the current code base. For this we want to separate page model ("PageStructureService" and model objects) from page actions.

The complete plan can be found here: https://docs.google.com/document/d/1RoGCnJSBXrvP0kdd0jGLzWNd6Cbv1ucCpbo0YLNUN5c