[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
What's worried about `FullyQualifiedClassName` part in the name is that it suggests specific class name resolution way of the resolver. Such detalization might not be good idea for interface method.

In particular first lines of method itself (when given class already matches something even without being prefixed by namespace) throws that FQCN logic mentioned in method name out of the window :)