added in sortingOrder

docs/angular-grid-grid-options/index.php

docs/angular-grid-sorting/exampleSortingOrder.html

docs/angular-grid-sorting/exampleSortingOrder.js

docs/angular-grid-sorting/index.php

docs/example.js

src/ts/entities/colDef.ts

src/ts/entities/gridOptions.ts

src/ts/gridOptionsWrapper.ts

src/ts/rendering/headerRenderer.ts

src/ts/rendering/renderedHeaderCell.ts

src/ts/rendering/renderedHeaderGroupCell.ts