Add integration tests for arrow selection

[javier-godoy]

The test can be something along the following lines, but I was not able to send keys on Grid

    $server.setSelectionMode(SelectionMode.SINGLE);
    $server.setArrowSelectionEnabled(true);

    assertThat($server.getSelectedRows(), equalToList());

    grid.sendKeys(Keys.DOWN);
    grid.sendKeys(Keys.DOWN);
    assertThat($server.getSelectedRows(), equalToList(2));

    grid.sendKeys(Keys.UP);
    assertThat($server.getSelectedRows(), equalToList(1));