Python: Fixed build on rhel6.
Core: Fixed offsetof.
Core: removed useless group_id from dnet_ids_init
Core: renamed offsetof to dnet_offsetof.
Merge pull request #242 from shaitan/recovery

Recovery: Added using wait_timeout provided by command arg.
Merge pull request #241 from shaitan/python

Python: Fixed build on rhel6.
Python: Added __len__ to elliptics.Data
Added ability to use common len() function for getting size of elliptics.Data
Merge pull request #243 from shaitan/python

Python: Added __len__ to elliptics.Data
Cpp: fixed write_data by chunks.
Fixed prepare size - for write with offset it should includes offset and file size
Cpp: Updated comments.
License: Updated Copyright.
Merge pull request #247 from shaitan/master

License: Updated Copyright.
Cpp: Extended comments and notes about write_prepare, write_plain and write_commit.
Merge pull request #246 from shaitan/clean

Cpp: fixed write_data by chunks.