Allow comparison of geo types, binary to null.

We currently state that operators can be used with types other than geo, stream, and binary, as these values are typically not comparable, but we don't say what can be used with these types..

It is valid to compare these values to null. This is handled in database systems, for example, by having "is null" and "is not null" operators, but since in OData we decided (after long debate) to use "eq null" and "ne null" to compare to null values (with appropriate null propagation rules). However, the current verbiage could be misinterpreted to mean that the common and useful case of comparing binary, stream and geo values to null is not supported.