Rename src/include files and folder

src/linkahead/entity.cpp

src/linkahead/file_transmission/download_request_handler.cpp

src/linkahead/file_transmission/file_reader.cpp

src/linkahead/file_transmission/file_writer.cpp

...kahead/file_transmission/register_file_upload_handler.cpp

src/linkahead/file_transmission/upload_request_handler.cpp

src/linkahead/info.cpp

src/linkahead/logging.cpp

src/linkahead/protobuf_helper.cpp

src/linkahead/result_set.cpp

src/linkahead/result_table.cpp

src/linkahead/result_table_impl.h

src/linkahead/status_code_description.cpp

src/linkahead/transaction.cpp

src/linkahead/transaction_handler.cpp

src/linkahead/unary_rpc_handler.cpp

src/linkahead/utility.cpp