predict_predicate_mention method forgets to change the prop_mentions_by_key

[hitzkrieg]

The predict_predicate_mention method in the file eval_predicate_mention.py takes a gold graph and returns the same graph with predicted predicate mentions instead of gold ones.
However it forgets to change the prop_mentions_by_key dictionary for the newly created graph (prop_mentions_by_key remains the old value). Also it would be helpful if the method also annotates the argument_mentions found from prop_ex.

Thanks :)

https://github.com/vered1986/OKR/blob/master/src/baseline_system/eval_predicate_mention.py#L67