Cell - Logger Component with winston

Replaces the default Logger of @celljs/core with one backed by winston.

The level comes from cell.logger.level (default info); cell.logger.winstonConfig is merged into the winston options. The per-request access log of @celljs/web is written at debug, so it is not printed by default; set cell.logger.level: debug (or CELL_BACKEND__CELL__LOGGER__LEVEL=debug) to see it.