Revision 409297

 - Added some of the intial infrastucture needed to be able to use that DataManager to do index file recovery.
 - ObjectMarshaller now avoids doing byte[] allocations.
 - We now store the data item's size in the index file so that when we load data from the data file using a 
   DataItem object, the data payload can be read in 1 io operation, previously an extra io was need to find
   out the size of the payload.