Fixed python bindings and added storing ids files in elliptics itself.

Python: fixed write_prepare, write_plain and write_commit - input arguments data_pointer has been replaced by std::string.

ioserv: at the start ioserv tries to read local ids file. If ids file is missed ioserv reads it from remote nodes. If ids file is missed on all remote nodes too, it would be generated and writed to remote nodes. For storing ids file it uses follow key: "elliptics_node_ids_addr", where addr is address of local node with port and family like "123.123.123.123:1025:2".