Revert "fix example type for lbfgs"

This reverts commit e2ce29fd7a599da0e751d6dcf9402699bf7bb41c.
Revert "using label_data in gd.cc"

This reverts commit 964650ee9184025f8a96620164c96cf714dca202.
Revert "made label type explicit for examples"

This reverts commit b46ca4d0ebe3e5d81b507a8477129f1a998e86bb.