Clarify that $ is the separator character which should be used for the external names of static nested classes

Various user-defined objects can be created which are bound to Java methods or classes via "external name" clauses. It's easy to mis-phrase the Java class name in the "external name" clause if the class is a static nested class. The affected objects include:

o Functions
o Procedures
o Types
o Aggregates

Consider the following class:

public class TestFuncs
{
public static final class Foo
{
public static double pow( double base, double power )

}
}

If the pow method is bound to a user-defined function via a CREATE FUNCTION command, its external name should be TestFuncs$Foo.pow, NOT TestFuncs.Foo.pow.

We should add a section to the Reference Manual clarifying how to phrase the external name if it includes a reference to a static nested class. The detailed sections for the various user-defined objects can then refer to this new section.