ISPN-4354 Unable to use custom keys/values with clustered caches in OSGi

Change the infinispan-core bundle headers to dynamically import * as the classloader on this bundle is used by default in the class resolver.
ISPN-4354 Unable to use custom keys/values with clustered caches in OSGi

Set the Dynamic-ImportPackage * header when repackaging the core bundle for the tests.
Add test for custom objects in cluster