Implement new Job flow

Rathern than just `corectl start` and `corectl stop`, support `corectl submit`, `corectl start`, `corectl stop`, and `corectl destroy`. The start and stop actions now only work on units that have been submitted to the coreinit cluster. A call to enable units will simply upload to the cluster and reserve the unit names. A stop will only stop the unit from executing, it will not remove the unit file from the cluster.