Property cardinality

[diegoberaldin]

It should be possible to specify, in the input model, the multiplicity of each descriptive fields in order to allow two different cases:

• if cardinality = n, at most n occurrences of the field can be found for each term/language/entry; (for n = 1 this is the actual situation for all fields)
• if cardinality = ∞, an arbitrary number of fields can be inserted for the same property.