Disabling option value should not remove the value if no issues use it

[Joe Mallon]

Current behavior: if a value is disabled and no issues use it, the value is removed from the database. This prevents an automatic updating of values that has been groomed - the deleted values will continue to show up in the list after every import.

[Holger Schimanski]

Validation is now done for Project Specific Select Field and Project Specific Multi Select Field, but not for Project Specific Select Field (simple).

Version 2.0.0 released.