Port most notebook model code over to be behind a service (#3068)

- Defines a new NotebookService in Azure Data Studio which will be used to interact with notebooks. Since notebooks can require per-file instantiation the provider is just used to create & track managers for a given URI.
- Inject this into notebook.component.ts and pass required parameters that'll be used to properly initialize a manger into the method. Actual initialization not done yet.
- Port over & recompile notebook model code
- Define most required APIs in sqlops.proposed.d.ts. In the future, these will be used by extensions to contribute their own providers.

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

@@ -7,10 +7,11 @@ import 'vs/css!./codeCell';
 import { OnInit, Component, Input, Inject, forwardRef, ElementRef, ChangeDetectorRef, OnDestroy, ViewChild } from '@angular/core';
 
 import { CommonServiceInterface } from 'sql/services/common/commonServiceInterface.service';
-import { CellView, ICellModel } from 'sql/parts/notebook/cellViews/interfaces';
+import { CellView } from 'sql/parts/notebook/cellViews/interfaces';
 
 import { IColorTheme, IWorkbenchThemeService } from 'vs/workbench/services/themes/common/workbenchThemeService';
 import * as themeColors from 'vs/workbench/common/theme';
+import { ICellModel } from 'sql/parts/notebook/models/modelInterfaces';
 
 
 export const CODE_SELECTOR: string = 'code-cell-component';