Full plumb through of Session support. Also fixed some test issues
- Load session and get necessary information in kernels list
- Run Cell button now works as expected
- Added a ToggleAction base class which can be used for anything that switches icons. I'd still prefer to have this be dynamic and as clean as the extension classes
- Fixed account test unhandled promise rejections (caused by incorrect / invalid tests) that made it hard to see all the test run output.
* Stop showing decorationsOverviewRuler in notebook code cells by setting hidden visibility in css
* Also change overviewRuler options in IEdtorOptions for safety
* address CR comments in css file
* Added toggle more actions to cell
* Resolve PR comments
-- Added INotificationService for notification msg
* Reduced ToggleMoreAction to smaller size. So the dropdown could be displayed closer to it instead of at the buttom of the cell.
* initial work for addig code and code cell type
* add cell model and create editor for each cell
* formatting
* fix resizing issue
* small changes
* address comment
