Java 7 diamonds
Non functional changes.

Fix typos in comments.
Use character instead of String where possible.
Java 7 diamonds
Use character instead of String where possible
Minor, non-functional code simplification
WICKET-5296 OnEventHeaderItem should remove 'on' prefix for the event name
WICKET-5295 UrlResourceStream#getData content-type detection relies on flawed logic in URLConnection#getContentType
WICKET-5294 MarkupCache ignores enforceReload flag