Template implementation of a registry reader that creates objects representing registry contents.
Typically, an extension contains one element, but this reader handles multiple elements per
extension.
To start reading the extensions from the registry for an extension point, call the method
readRegistry.
To read children of an IConfigurationElement, call the method readElementChildren
from your implementation of the method readElement, as it will not be done by
default.
Provides a consistent mechanism to interact with StructuredViewers over time.
The Common Navigator framework attempts to defer the loading of extensions,
which also means defering the loading of Content Providers.