Reviewed-by: darcy, weijun

Reviewed-by: anthony, ant, dcherepanov

Summary: Replace calls to Logger with sun.util.logging.PlatformLogger
Reviewed-by: prr, art, alexp, dcherepanov, igor, dav, anthony

Summary: mainAppContext, isDisposed, and numAppContexts has beem made volatile.  mostRecentThreadAppContext has been rewritten using ThreadLocal.
Reviewed-by: art

Summary: Added synchronization to AppContext.getAppContexts()
Reviewed-by: art

Summary: AppContext.dispose() should be ready to get exceptions during disposal of toplevels.  Also now we mark windows peers as destroyed when native object has been destroyed.
Reviewed-by: art