[WIP] Enhance getPage in PageFactory

This is the first WIP commit, just a draft.
* Only the prefix logic is implemented and I am not sure  if the DefaultPageLocator should return an FQCN or a `Page` instance (in this case it requires a `PageFactory`).

Closes #12
Are you sure that we should use `FullyQualifiedClassName` in method name? I thought we just call it `resolvePage($page_name)`.