Garbage collection process for binaries should be configurable

The ModeShape engine has a garbage collection process that cleans up non-scoped locks and unused binaries. These tasks were registered in the engine and are therefore not configurable for each repository.

However, while the lock cleanup could continue to be executed every 5 minutes, cleaning up unused binaries probably shouldn't be done nearly that often because:

1. on larger repositories it will likely take longer than 5 minutes to run
2. it only reclaims unused persistent storage
3. it's probably desirable to run off-hours

Therefore, we should change how the binary garbage collection is configured. We probably want to allow specification of when and how frequently it is to be run. For example, we could allow setting a start time (e.g., maybe ISO 8601 format??) and a frequency (or interval). Perhaps the default start time should be midnight local time, and the default interval is 24 hours.

Also, if each repository had this configuration, then the ModeShape engine could ask the JcrRepository to register with the engine's executor any scheduled processes near the end of the repository startup process.