#431 Concept and relation names with '_' may cause protype problems

[Martijn Schrage]

Since showHSName disambiguates relation names by appending source and target concept, separated by underscores, relation and concept names containing underscores may violate injectivity of this mapping. In other words: r[A_B*C], r[A*B_C], en rA_[B*C] all get the same name "rel_rA_B_C", which creates a problem during table lookup in the prototype.

To fix this, we need to disallow '_' in relations and concepts in the parser/scanner.