Revision 168630

o Added duplicate check for mojo descriptor Parameters
o changed the exception(s) throws during mojo descriptor extraction to be derivatives of InvalidPluginDescriptorException
o changed PluginConfigurationException in plugin.descriptor to InvalidPluginDescriptorException
o changed all "true".equals(something) to Boolean.valueOf(something).booleanValue()
o added validation of 'modelVersion' back to [Default]ModelValidator
o Fixed/added tests for new 'modelVersion' validation
o changed all requiresXXX in MojoDescriptor to XXXRequired, and getRequiresXXX():boolean to isXXXRequired():boolean to help maintain bean-ness for future use