Map features select all toggle

[boothym]

Add the option to deselect all of the map features, instead of having to deselect each of them individually.
Something like this image - the text could change to select all once the check box is ticked, or have two separate options.

Useful when editing an area with lots of objects or where you don't want the way/area you are drawing to snap to another object.

[bhousel]

Thanks! this is a duplicate of #2904