* Added hover support, adding box shadow and light outline on hovering and the "more actions" button showing on hover
* Added box shadow for dark themes (hooray!)
* Remove border from everything but the code cell unless a cell is selected or hovered over. This ensures this looks like a document
* Fix high contrast theming issues.
* 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 toolbar work
- This is in-progress and needs additional fixes
* Resolve PR comments
* Added empty kernel and hook up with Kernel dropdown
* Resolve PR comments
* 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
