Extensions to spring-batch's RetryTemplate for retrying Callable as well as classifying exceptions as retryable based on a predicate, rather than instance type.

In particular, this adds the following capability:

1.  Support for the Callable class within the ExtendedRetryTemplate
2.  A Classifier instance which is based on guava predicates
3.  Some useful predicates
4.  A retry policy which is based on a generic exception classifier, rather than the existing SimpleRetryPolicy which assumes a Map based approach to determining exception classification.