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

Upgrade to latest revisions of jQuery.
Additionally add the source map files for debugging in production mode.
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

Move the constant for VERSION_1 to JQueryResourceReference, so we don't forget to update it next time.
Simplify DynamicJQueryResourceReference.