allow pluggable data container in infinispan

In relation to http://community.jboss.org/message/529586#529586
Users might want to write their own data container and be able to plug that in infinispan. Implementing this would require:

• change configuration to support an dataContainer element perhaps under "eviction" elements. This will be passed to DataContainerFacvtory, which will build an instance of the class and pass it back.
  Actually, in order to allow parameters to this container, it can look like:
  <eviction wakeUpInterval="500" maxEntries="5000">
  <dataContainer class="custom.data.Conatiner">
  <properties>
  <propery name="configParam" value="configValue"/>
  </properties>
  </dataContainer>
  </eviction>