More consistency checking for relationship group records

Added the following checks:
o RelationshipGroupRecord has invalid rel type id
o RelationshipGroupRecord has invalid next pointer
o RelationshipGroupRecord chain is unsorted
o RelationshipGroupRecord refers to relationship that is not in use
o RelationshipGroupRecord refers to relationship that is not first in its
  chain
o RelationshipGroupRecord refers to relationship that is of a different
  relationship type than its group
Merge pull request #2035 from tinwelint/2.1-cc-relgroups

More consistency checking for relationship group records