Implement `func disjoint(_ other: Geometry) -> Bool`

[tonystone]

A comprehensive test suite needs to be developed for all variations of geometries for the disjoint function.

[tonystone]

Add to protocol Geometry and all implementing types with the syntax:

    //
    ///- Returns: true if this geometric object is “spatially disjoint” from the other Geometry.
    ///
    func disjoint(_ other: Geometry) -> Bool