Make DG Toolkit 4.x Wicket usage CSP compliant

[nmandrescu]

https://ci.apache.org/projects/wicket/guide/9.x/single.html#_content_security_policy_csp

[nmandrescu]

To make the app also CSP compliant wicket-bootstrap-extension has to become CSP compliant (affects BootstrapFileInput, ToolkitSummernoteEditor and likely other). Reported an issue, however it seems this lib is not plannning to become CSP compliant anytime soon.