Rewrite worker function as a class.

Signed-off-by: Chris Lamb <chris@thread.com>
Setup @property.setter on Process

Signed-off-by: Chris Lamb <chris@thread.com>
Use self.name wherever possible.

Signed-off-by: Chris Lamb <chris@thread.com>
Make queue runner idempotent - dying or killing workers just starts them again.

Signed-off-by: Chris Lamb <chris@thread.com>