Merge pull request #395 from shaitan/lts

Session: added checking groups list for emptiness at iterator operation.
v2.24.15.12
common: get rid of yars unused history maps
common: get rid of yars unused history maps. Convert IO time in dnet_convert_io_attr()
trans: added IO debug into dnet_process_cmd_raw() and to transaction destruction
v2.24.15.13
trans: also print total size for IO commands when transaction has been processed on server and destroyed on client
trans: more IO transaction log cleanups