Add CRaC support

[fipro78]

I would like to add CRaC support to the Jetty bundle. Using CRaC you are able to create a checkpoint of the application at a certain point of time, and then restore the application, which avoids the warmup phase.

Using the org.crac API it would be possible to add CRaC support directly in the JettyBackedWhiteboardComponent to register a Resource, without introducing a dependency that could not be resolved in different operating systems. And it does also not introduce a runtime dependency or issue, because the org.crac API tries to access the CRaC classes via reflection, and if it is not found, it will use a dummy implementation.

https://github.com/CRaC/org.crac