[UX] Update grid padding when td of grid is containing a widget component in Material theme

[elena-gancheva]

Currently the design for gird in Material Theme is with 16px padding for both left and right sides (when there is widget component as datepicker or combobox in grid's td of an k-editable-row).

Check the image for reference:

This is consuming too much space, which is critical for the grid usage, because of the big amount of data it's displaying. We discussed with @lkarakoleva that in this case, we can reduce spacing to: padding-right: 4px of the tds and update the design psd file of the grid.

Related to: telerik/kendo-themes#351

//cc: @ipeshev @gyoshev @joneff