The NetBeans plug-in file, layer.xml, has some issues. The following is the 
revised design for the plug-in file:

A JBI component has:
   - a JBI component ID (key)
   - a description
   - a component type

A wsdl extension, i.e., the schema file element, has:
   - an xsd file
   - a default namespace (may be shared w/other wsdl extensions) [added as a 
required attribute]
   - a default prefix (may be shared w/other wsdl extensions)
   - a JBI component ID (may be shared w/other wsdl extensions) [added as a 
new attribute]

A extensibility definition, i.e., the extensibility element,  has:
   - an xsd file name
   - a wsdl element name
   - a localization bundle
   - an icon 

We need to modify CompApp/CASA to support this change using the XML model 
implmented by the WSDL editor UI.