Contextize PageRenderingHooks

* Utilize more fully context received from hooks
* Instead of saving various parts of context locally, become a context provider.
* The above allows to initialize parts of context only when needed, helping prevent
  recursion loop in Language initializaton.
* Renamed PageRendering::getConfig to getZeroConfig to avoid overriding
  base method

Change-Id: I728ac60806e528fbd7d2ffd20c743d1fc5deb820