[ADF-2541] reset datatable selection when rows are changed from code (#3410)

* reset selection when rows are replaced from code

* code fixes

* unit test updates

* visualise selection count for testing purposes

* make row selection api public

* remove question mark from the event name

lib/core/datatable/data/datatable-adapter.ts

@@ -18,8 +18,11 @@
 import { DataColumn } from './data-column.model';
 import { DataRow } from './data-row.model';
 import { DataSorting } from './data-sorting.model';
+import { Subject } from 'rxjs/Rx';
 
 export interface DataTableAdapter {
+    rowsChanged?: Subject<Array<DataRow>>;
+
     selectedRow: DataRow;
     getRows(): Array<DataRow>;
     setRows(rows: Array<DataRow>): void;