BUG-868: Migrate to SchemaContextListener

SchemaServiceListener is deprecated, SchemaContextListener is its new
name. The class hierarchy allows for incremental migration.

Change-Id: I15d495d805eb7a08c3bcd3ab0cf8b5a8d2797db5
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-868: Migrate to SchemaContextListener"