Functions for alternative password

  - create alternative password
  - delete alternative password
  - manage alternative password (create and delete work with this
    method)
  - using attribute user:def:altPassword:namespace

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NEED TO DO AFTER MERGING:
1] create new attributeDefinition user:def:altPassword:* (all
possible login namespaces)
2] set rights for this attribute
3] add these information to the changelog!!!