WICKET-4686

Make it possible to use named mandatory and optional parameters in the url mounted with PackageMapper
Merge branch 'master' into sandbox/WICKET-4686
WICKET-4686 MountMapper does not support correctly parameter placeholders

Remove duplicated code and add javadoc
Java 7 diamonds and javadoc fixes
Remove useless call to redirectFromHomePage().

redirectFromHomePage() is called in org.apache.wicket.core.request.mapper.MountedMapper#parseRequest() where org.apache.wicket.core.request.mapper.MountedMapper#checkHomePage() is also used.
WICKET-4686 MountMapper does not support correctly parameter placeholders

Revert the null-yfing of the page parameters.
If there is no listener interface then everything is fine with the parsing of the parameters
Non-functional - fix comments
Remove an override of a method that does nothing different than its super
WICKET-4686 MountMapper does not support correctly parameter placeholders

Nuke MountMapper and related classes. They are not used anymore.