Changes done for GEB-310 - Support navigating to page instances in addition to classes

Following changes were done:

- Extracted Interfaces for all the support classes.
- Added Uninitialized support implementations for the said interfaces
- Added PageInstanceNotInitializedException class.
I thought about it but didn't do that because it required renaming existing files. I will do the necessary changes. Just wanted to confirm that you want this for all support files?