[gridpro] Add editCell(..) method to programmatically activating cell editor

[TatuLund]

Consider use case where you have e.g. button or other method to add a new row to the editor. You would like to programmatically open the cell in editing mode on the newly created row.

e.g.

gridPro.editCell(..);

Should it have overloading for different ways of indicating the cell, e.g. int, int for column, row index, String, int for column id, row index, String, T for column id, item.

gridPro.editCell(0,0);
gridPro.editCell(columnId,item);
gridPro.editCell(columnId,0);

(This was possible with Vaadin 8 using Grid FastNavigation add-on).

[rolfsmeds]

Related: #1219

[sirbris]

Does any workaround (via js?) come to mind?