Add support for manual configuration of scheduled jobs

To add jobs to the scheduler you currently need to make calls to the RepositoryScheduler service interface. This will persist the job in the repository.

It should also be possible to manually add jobs and triggers to the repository by creating the required JCR nodes below the scheduler module configuration, so that people can add jobs by using the console or via bootstrap configuration. The scheduler should "pick up" such manually added configuration.

The change is minimal, and the reason this doesn't already work is that internally the scheduler relies on the computed property "hipposched:nextFireTime" to find triggers to fire. What needs to be done is simply compute these properties and add them when someone manually adds a job and/or a job trigger.