Add the abillity to expand all details

[alocin98]

In our project, we have the requirement to expand all rows with one control. The best place to add this feature would be to have a carret in the header of the datagrid. What do you guys think about adding tis feature? We could propose a solution if needed.

Link to the code:

ng-clarity/projects/angular/src/data/datagrid/datagrid.html

Line 61 in 34cdc7a

<!-- header for carets; only displayType if we have at least one expandable row in datagrid -->