Regroup kernel information in a KernelInfo class

[pith]

Create a KernelInfo class which regroup all the info useful for debugging/logging, for instance:

public interface KernelInfo {
    Map<String, Plugin> plugins();
    UnitModule unitModule(Class<? extends Plugin> plugin);
    UnitModule overridingUnitModule(Class<? extends Plugin> plugin);
    UnitModule nonGuiceUnitModule(Class<? extends Plugin> plugin);
    UnitModule nonGuiceOverridingUnitModule(Class<? extends Plugin> plugin);
    GlobalModule globalModule();
    Set<URL> scannedURLs();
}

This class will be provided by a new method on the kernel:

public interface Kernel {
    ...
    KernelInfo getInfo();
}