Fixing selection problem with mobile scroll

These changes allow someone to scroll the grid on a mobile browser without inadvertently selecting a row, by adding a timeout. Short touches will select a row. Long touches, like a scroll, will not. The click event behavior is unchanged, so desktop browsers will behave the same. Related to Issues  https://github.com/angular-ui/ng-grid/issues/1759 and https://github.com/angular-ui/ng-grid/issues/1551 and previous commit https://github.com/angular-ui/ng-grid/commit/4bb2d6996aad6463155bcd01b1521441cab45270