The first iteration of uc logs command:

• print logs from all active replicas of the service (--tail 100 by default to not overflow the terminal)
• stream logs with -f
• one or multiple services
• chronologically sorted by timestamp using low watermark approach
• --since and --until to specify the time range like in docker logs
• colours to highlight different machines when viewing one service or different services when viewing multiple-services

closes #12