Performance, recovery and extended header fixes.


* Improved performance of blob_read().
* Test for write with DNET_IO_FLAGS_COMMIT flag set.
* Fixed LOOKUP queries with extended metadata.  
Now it returns proper size, offset and also uses timestamp from extended metadata.
* Fixed dnet_send_file_info_without_fd behavior.  
Now it sets file name to '\0'
* Recovery 'merge' fixes for recent merge
* Recover ts and user_flags along with data itself
* Yet another file reordering of python recovery module