The registration process must implement the hierarchical structure of groups

[SergioArbarviro]

The current groups existing in the LDIF descriptor are:

• ordinaryMembersGroup
• cooperatorsGroup
• boardMembersGroup
• mediationArbitrationCouncilGroup

These groups are structured hierarchically: ordinaryMembersGroup includes cooperatorsGroup includes (boardMembersGroup union mediationArbitrationCouncilGroup)

The registration process must implement this hierarchy:

• when a person registers as an Ordinary Member of the Community, s/he is included in the ordinaryMembersGroup;
• when a person registers as a Cooperator, s/he must be included in both the cooperatorsGroup and the ordinaryMembersGroup;
• only members of the cooperatorsGroup are allowed to be promoted to members of the boardMembersGroup or of the mediationArbitrationCouncilGroup.

[michaellaunay]

See #74