chore(views): refactor Elgg_ViewsService to store absolute paths

Refs #6844

TODOs:
 * [ ] Add tests for global code that depends on this service.


This is a major refactoring of Elgg_ViewsService. I know for sure that the global functions are broken as a result of this, but we don't have tests for them. Looking for early feedback, especially in regard to **what tests we can add**.

DO NOT MERGE