Implement Session support through the extension host (#3228)

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.

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

@@ -39,6 +39,11 @@ export class CodeCellComponent extends CellView implements OnInit {
 	ngOnInit() {
 		this._register(this.themeService.onDidColorThemeChange(this.updateTheme, this));
 		this.updateTheme(this.themeService.getColorTheme());
+		if (this.cellModel) {
+			this.cellModel.onOutputsChanged(() => {
+				this._changeRef.detectChanges();
+			});
+		}
 	}
 
 	// Todo: implement layout