Integrate first SQL Notebooks Bits into Master (#3679)

* First crack tsql notebook (no output rendered yet)

* getting messages back

* intellisense working first cell, no connection errors

* sql notebook cell output functioning

* Latest SQL noteobook changes

* Undo change to launch.json

* Plumbing providers through

* Kernels shown from multiple providers, can switch between them. No mementos yet

* Ensure we have a feature flag for SQL notebooks, ensure existing functionality still works

* Fix tslint duplicate imports issue

* Addressing PR comments

* second round of PR feedback to cleanup notebook service manager code

* merge latest from master

src/sql/parts/notebook/cellViews/outputArea.component.ts

@@ -33,9 +33,9 @@ export class OutputAreaComponent extends AngularDisposable implements OnInit {
 		this._register(this.themeService.onDidColorThemeChange(this.updateTheme, this));
 		this.updateTheme(this.themeService.getColorTheme());
 		if (this.cellModel) {
-			this.cellModel.onOutputsChanged(() => {
+			this._register(this.cellModel.onOutputsChanged(() => {
 				this._changeRef.detectChanges();
-			});
+			}));
 		}
 	}