JobStoreFactory determines table name

[paul-m]

As part of an effort to decouple jobstore table names from implementation class names, we want the JobStoreFactory to determine table names. This will suport consistency in future changes to this system.

This PR:

• Moves table name logic out of JobStore and into JobStoreFactory.
• Replaces JobStoreAccessor with JobStoreFactoryAccessor to facilitate handling of deprecated jobstore table names.
• Modifies JobStoreUtil to use JobStoreFactoryAccessor.
• Adds and modifies tests to prove this all works.
• Improves docblocks.