Create a TaskQueueExecutorFactory and TaskQueueScheduledExecutorFactory

These executors will not spawn separate threads, but hook in to Google's TaskQueue API

http://code.google.com/appengine/docs/java/taskqueue/overview.html

This will enable Infinispan to run without spawning any additional threads, thereby enabling it to run on Google's App Engine runtime.

Will need to expose a URI (/taskqueueexecutor ?) which is invoked to process arbitrary Callable/Runnables. May need to use the DataStore to store the actual Callable/Runnable, and pass the taskqueueexecutor the key of the stored object.