reexport datasource

Author: andrewseguin

src/cdk/table/public_api.ts

@@ -16,6 +16,9 @@ export * from './table';
 export * from './cell';
 export * from './row';
 
+/** Re-export DataSource for a more intuitive experience for users of just the table. */
+export {DataSource} from '@angular/cdk/collections';
+
 const EXPORTED_DECLARATIONS = [
   CdkTable,
   CdkRowDef,