Review places where argument exceptions are thrown

[jng]

There are still some places in the MapGuide codebase where naked MgNullArgumentException objects are thrown.

Cases where these are thrown provide no useful context for the developer as it lack key important information: The name of the argument that is null.

We already have a CHECKARGUMENTNULL() macro to inject the argument name when throwing the exception. We need to find all cases where such exceptions are still manually thrown and replace them with this macro.