if a bridge needs to modify some of the data that were initialized
there, ::__construct() should be used instead.
Signed-off-by: Pierre Mazière <pierre.maziere@gmx.com>
Some bridges used getName() and getURI() to put information into the
metadatas. Instead the metadatas should be initialized with data and
(not yet done) returned by default via getName() and getURI().
Many bridges implemented getDescription() which is only applicable for
bridges extending RSSExpander.
Functions that are not part of the abstract class or interface should
be in private scope for better readability.