more options for XML export

[DavidLeoni]

Currently Diversicon exports to XML only the normalized version of the db (so for examply exports only canonical relations like hypernym and not hyponyms). If database is not normalized outputs whatever it has with a warning.

We should make the behaviour customizable with:

• flag to include transitive closure
• flag to include non-canonical relations
• flag to export the original xml almost as it was at import time.