WICKET-5208 Contribute jQuery 1.x or 2.x depending on the user agent

Introduce DynamicJQueryResourceReference - a res ref that decides which version of jQuery to contribute depending on the user agent.
WICKET-5208 Contribute jQuery 1.x or 2.x depending on the user agent
WICKET-5208 Contribute jQuery 1.x or 2.x depending on the user agent