refactor(registry): Unexport Registry.GetMachineAddrs method
refactor(registry): Unexport Registry.Etcd field
refactor(registry): Add method documentation to Registry
refactor(registry): Drop unnecessary Registry.GetJobPayload method
refactor(registry): Rename Registry.GetScheduledJobs to GetAllScheduledJobs
refactor(registry): Rename Registry.GetMachineJobs to GetScheduledJobs
refactor(registry): Rename Registry.SaveJobWatch to AddJobWatch
refactor(registry): Rename Registry.UpdateJob to SaveJobState
refactor(engine): Move ClaimJobWatch functionality to Registry
fix(dispatcher): Correct event names in logs
fix(dispatcher): Handle EventJobWatchDeleted properly

* add a handler for EventJobWatchDeleted to the Dispatcher
* store JobWatch objects in the Dispatcher in a map so they are easiliy
  addressable when they need to be removed
feature(coreinit): Add -debug flag to coreinit binary
refactor(registry): Clarify the methods used to remove a JobWatch
refactor(dispatcher): periodically re-claim job watches
refactor(engine): remove scheduler field from Engine
refactor(engine): break apart JobWatch logic into JobWatcher struct
fix(agent): Unlink unit files when jobs are stopped
refactor(stop): Stop JobWatch by name
refactor(JobWatcher): track schedules for ease of Job deletion
refactor(JobWatcher): cleaning up code for style purposes