* Fix#5238 Notebooks should support relative links
- Added detection of relative #links inside notebooks
- Added handling of these, at least for current notebook
Not handled: open other notebook & scroll to position.
* Improve notebook link handling
- Single click now works for links inside Output areas
- Command links in untrusted notebooks have link color
- Refactored to use directive so code is in 1 place and can be easily
added elsewhere if needed
* Removed unneeded service from constructor
* Log telemetry when all markdown cells rendered
* Enable referencing previous telemetry timestamps
* Fix broken unit test to do a null check
* Undo loading icon changes in textcelll
* Addressing PR comments
* PR comments II