Introduced generated unique id's, instead of the pointer address to avoid 64bit->32bit truncation issues
Use serializer->getUniquePointer instead of directly using a pointer
moved ChunkUtils::getNextBlock to bFile::getNextBlock.
Moved 'TEST_BACKWARD_FORWARD_COMPATIBILITY' to bDNA.cpp. Enable the define for further testing of .bullet format
Removed duplicate definitions and use the one in LinearMath/btSerialization.h
