Added a SentenceTriple Class

This is for compact representation of following information from
candidate sentences to supply for relation classification:

1) sentence
2) relation type
3) provenance

Signed-off-by: Vidhoon Viswanathan <vidhoon@cs.utexas.edu>
Added SentenceDouble class

For ease of processing candidate sentences

Signed-off-by: Vidhoon Viswanathan <vidhoon@cs.utexas.edu>
Virtual IR changes

Adding changes to by pass stanford KBP system IR
and use candidate sentences from LSV system.

Signed-off-by: Vidhoon Viswanathan <vidhoon@cs.utexas.edu>