Add support for predicates when asserting a lookup-matches

[Seddryck]

Currently, NBi is supporting strict equality when validating a lookup-matches. With #470, it should also be possible to use some tolerance but it will still be an equality that will be tested. It should be possible to use any predicate to assert that the value contained in the dataset is related to the value of the other dataset.

<inclusion>
  <include candidate="previousAge"/>
  <predicate operand="[age]" type="numeric">
      <more-than>[previousAge]</more-than>
   </predicate>
</inclusion>

This feature is relying on the implementation of #472