Add Keyboard shortcut for clearing check boxes

[KiwiCNC]

It would be advantageous to add a keyboard shortcut for clearing the check boxes by column so that if using an interactive foot switch to check the boxes the you could do a long press at the end of you build to clear the boxes ready for the next board assembly. This would remove unnecessary movement to grab a mouse, select the column and then double click. then move back and prepare to place more parts, improving cycle time and manufacturing processes. Maybe a simple 'S' for sourced or 'P' for Placed, ect to clear the column.