Add file comments for each source module

[deepthidevaki]

Each file contains only the copyright info. It would be good to have a 1-5 lines at the top of each file, describing the module.

• [ ] antidote_app
• [ ] antidote_error_monitor
• [ ] antidote_node_event_handler
• [ ] antidote_pb_process
• [ ] antidote_warning_monitor
• [ ] binary_utilities
• [ ] binary_utilities
• [ ] clocksi_downstream
• [ ] clocksi_materializer
• [ ] clocksi_readitem_server
• [ ] clocksi_vnode
• [ ] cure
• [ ] dc_meta_data_utilities
• [ ] dc_utilities
• [ ] inter_dc_manager
• [ ] inter_dc_query_response
• [ ] inter_dc_query_response_sup
• [ ] inter_dc_txn
• [ ] log_utilities
• [ ] logging_vnode
• [ ] materializer
• [ ] materializer_vnode
• [ ] zmq_utils

[palash25]

@deepthidevaki @albsch I have a made a small PR can you PTAL?