Implement $geoNear for MultiPoints and GeometryCollections containing a single point

Can't run $geoNear queries for a MultiPoint like this:

{ 'type' : 'MultiPoint', 'coordinates' : [ [1, 1] ] }

or a GeometryCollection like this:

{ 'type' : 'GeometryCollection',
'geometries' : [

{ 'type' : 'Point', 'coordinates' : [1, 1] }

]
}