Add Logging ; Fix Broken Maintenance Context

[axelKingsley]

• Fixes the maintenance routine to use a context that doesn't have a cancelled parent
• Adds a Logger to ChainsDB
• Uses the Logger to describe maintenance behaviors
• Tweaks the Trivial Test a bit (adds a 30s period where the network runs)
• Adds a delay between AddL2 calls on the Supervisor, as that API is not very stable
• Adds client code for Supervisor Start and Stop

I wanted to add some logging to witness Maintenance loops doing things when working on event-log emissions in SuperSystem. In doing so I found that the maintenance loop was using a context with a closing parent.