WICKET-5237 Wicket generates invalid HTML by expanding col tags

Add unit test for non-void elements too
Fix 'inputchange' event handling in IE
WICKET-5246 Use ModalWindow settings for unloadConfirmation
WICKET-5247 don't map handler when value for required placeholder is
missing
Fix jshint warnings
Java 7 diamonds in wicket-util
Java 7 diamonds for wicket-request module
Java 7 diamonds for wicket-ioc
Java 7 diamonds for wicket-guice
Java 7 diamonds for wicket-spring
Java 7 diamonds for wicket-cdi
Java 7 diamonds for wicket-auth-roles
Java 7 diamonds for wicket-common-tests
Java 7 diamonds for wicket-datetime
Java 7 diamonds for wicket-devutils
Java 7 diamonds for wicket-examples
Java 7 diamonds for wicket-extensions
Java 7 diamonds for wicket-jmx
Java 7 diamonds for wicket-velocity
Java 7 diamonds for native websocket