Replace batching="true|false" with <transaction mode="BATCH"/> in infinispan subsystem schema/model

Currently, one enables use of Infinispan batching via the batching="true" attribute. The implications of batching have evolved over time, but currently batching uses the BatchModeTransactionManager, which makes it incompatible with a <transaction mode="..."/> other than NONE.

To resolve this mutual incompatibility and to remove any ambiguity, I propose replacing the batching attribute with a new transaction mode, i.e. <transaction mode="BATCH"/>.

The complete list of transaction modes would now be:
NONE: the cache is not configured with a transaction manager
BATCH: the cache is configured with a BatchModeTransactionManager
NON_XA: the cache is configured with WF's transaction manager, but will interact via Synchronizations
NON_DURABLE_XA: the cache is configured with WF's transaction manager and will interact via an XAResource w/out recovery.
FULL_XA: the cache is configured with WF's transaction manager and will interact via an XAResource w/recovery.