Add jobservice and job types

[riethm]

Alternative to #257 (abandoned?) that addresses issues noted in that PR:

• Rename ServiceCapabilities to JobServiceCapabilities (consistent with schema)
• Rename service capability ServiceEnabled to Scheduling (consistent with schema. ServiceEnabled is a property of JobService rather than a capability)
• export ListReferencedJobs (consistent with other gofish library services)
• Move GetJob and ListReferencedJobs from jobservice.go to job.go (consistent with other gofish library services)