Sentence clone method

[ktuukkan]

marc-pan via sourceforge.com: Parser doesn't provide public clone method, and i don't find elegant way to do it. The only way that i find to do it for the moment is;

SentenceFactory.getInstance().createParser(sentence.toString())

but it's not really efficient.

[ktuukkan]

This turned out to be non-trivial, postponing for later release.