Feature/#105 match logfiles to rooms

[plaza-in-a-heatwave]

Allow lognames to be named according to config items:

• all log() messages made before parsing completes use a unified logfile.
• unified logfile is writable by all cadesim instances.
• all log() calls after parsing are redirected to per-instance logfiles.
• instance logfiles are nameable according to config or derived values.

Minor other things:

• change logger case to be more consistent
• move updater code, welcome text so that they appear in the instance log
• move shutdown hook so that it only uses the instance log
• reduce spam from updater

[plaza-in-a-heatwave]

Self-merging as time is a little short :grimacing: