Description
Implementation for deregisterAll(Class category):
1. Find the ProvidersMap instance for that category.
2. Find all the providers that have been registered in this ProvidersMap, and perform RegisterableService.onDeregistration() method for each of them, and remove them
Implementation for deregisterAll()
1. Find all the categories
2. reuse deregisterAll(Class category) method for each of them.
Spec - http://java.sun.com/j2se/1.4.2/docs/api/javax/imageio/spi/ServiceRegistry.html#deregisterAll()