Update train-model.perl

When I was working with factored models, my experiments failed. After some invistigation, I discovered that the delimiter is hardcoded in several places to "|" so I changed it to $___FACTOR_DELIMITER
Merge pull request #59 from akholy/master

Update train-model.perl
modify DALMwrapper.
create ResetWeights(). Only for dense weights
reset sparse weights
need to zero out all weights, especially sparse weights
update last weight override
don't check object pointer before deleting /Markus Elfring
xml parsing for source syntax