Migrate to PrimeFaces 15

Migrate from PrimeFaces 14 to 15 by upgrading primefaces and primefaces-extensions to 15.0.x and making the changes in the migration guide that keep the behaviour of 14. What needs a person's judgment, including a primefaces version that cannot be upgraded, gets a warning saying what to do, unless the module already started on the PrimeFaces release with that change. It runs only on a repository where a module resolves primefaces 14 or 15.