Updates to SCV Constraint definitions

The configuration screen for SCV Constraints has been updated with these conditions for a better alignment with different constraint types:

• One of the active keys such as Primary Key (PK), Business Key (BK), Export Key (EK), Refresh Key (RK) or Hash Key (HK) can be defined on each SCV table. A defined PK, BK, EK, RK or HK on a table is enabled and cannot be disabled.
• When defining a new constraint, the list field on constraint type now displays only the possible types (i.e. the constraint types for which no constraint has been defined yet)
• Multiple Foreign Keys (FK) can be defined on each SCV table and defined FKs can be disabled (behavior did not change)