WICKET-4879: null check for the resource
WICKET-4889: added a constructor that takes Serializable
WICKET-4889: added a constructor that takes Serializable

Fix a javadoc link.
Add a TODO to remove the constructor that accepts String in Wicket 7. Deprecating it now will lead to ugly warnings in the user apps.
WICKET-4884 keep locale untouched but do custom conversion instead
WICKET-4873 Support different session id parameter
WICKET-4891 handle composed context and filter paths, remove all prefix
or none
WICKET-2128 use ${label} consistently
Use the passed event name instead of using the hardcoded "click" (fixing a copy/paste error).

Mark an obsolete method officially as deprecated. It is not used since Wicket 6.0.0
WICKET-4892 Provide helpful exception message in RequestCycle#urlFor(Class, PageParameters)
WICKET-4887 Use a Set to keep the supported wicket elements in WicketTagIdentifier
WICKET-4890 Bad validation messages after WICKET-2128

Improve the text in Bulgarian resource bundle
WICKET-4890 Bad validation messages after WICKET-2128 for _en, _de and _de_CH
Fix broken Javadoc link
WICKET-4895 WicketRuntimeException: addOrReplace for feedback panel does not clear Component.FEEDBACK_LIST - feedback from replaced component causes error.
Use Args.notNull()
WICKET-4890 properties for _de_CH and _fr
WICKET-4899 Strings#escapeMarkup() escapes quotes already
Fix the message of debug log
Add #toString() for UrlResourceReference.
WICKET-4902 ConcatBundleResource should use the respective ITextResourceCompressor