- Scheduler implemenation -> components
- types -> toplevel scheduler package
- integration_test.go -> integration

- rename scheduler.{operations -> components}
- move each component into its own directory with doc.go file, for proper
  access isolation

- rename types.Framework -> types.Scheduler
- rename MesosScheduler -> Framework
- transform MesosFramework into independent Scheduler glueing all scheduler
  components, implementing types.Scheduler and owning the task registry