Massive progress on implementation of the Lab Server Controller.

Changes to the Control Sheet:
 * Clean up the Control Sheet information model and add a validity
   check
 * Dropped the World Seed field, as we don't have any code to handle
   it yet.
 * Also brought the field names in the Control Sheet example,
   documentation, and the code into sync.
 * Check for whether the appropriate headers are present in the
   Control Sheet or not.
 * Moved to Commands from State. Simplified the processing.

Changes to the Controller itself:
 * Implemented the "RUN" and "DOWN" instance command.
 * Implemented the "show" and "process-commands" controller subcommands.

Minor Changes:
 * Improve logging formats, add timestamp when --debug is used.
 * Cleaned up the object model a little bit.
 * Other documentation updates.

Next up, implement remaining commands and work on pushing updates back
into the Control Sheet in the Google doc.