PatientProgram: When completing a program, the end date of the most recent state in each workflow should be set to the completion date of the program

When completing a program, the end date of the most recent state in each workflow should be set to the completion date of the program. (Right now the end date always remains null).

Also, if the completion date of a program is ever set back to null ("uncompleting the program") then the end date of the most recent state in each workflow should also be set back null.

Criteria:

• When completing a program, the end date of the most recent state in each workflow should be set to the end date of the program
• When uncompleting a program (setting end date to null) the end date of the most recent state in each workflow should be set to null
• Tests should be added to PatientProgramTest to verify both of the above criteria

This functionality should be added at the same time as TRUNK-5228 and TRUNK-5229 for consistency.

There was talk of backporting these, features, but I think it's fine to just apply them to the latest master at this point.