WICKET-5635 Provide a way to modify ResourceReferenceRegistry.DefaultResourceReferenceFactory externally to be used by wicket-bootstrap-less

(cherry picked from commit 6154fd6aae702ec5c23d39f6ac3ae9593da4d3b9)
WICKET-5636 Submit repeated form components on stateless forms

(cherry picked from commit e50f298107ea2d8526a201d44a7200240747e80b)
WICKET-5648 CookieUtils - add #loadValues(), make #getCookie() public, properly initialize from the defaults

(cherry picked from commit b5e29819b1aa75ef8648c6ebaf0b5ebf72bdb2da)
Optimize imports
Minor improvements:

- Java 7 diamonds
- append char instead of String
- do not calculate the idValue in a loop