[MRG] Remove deprecated parameters whose removal was scheduled for 0.15

Some deprecated parameters were scheduled for removal for 0.15 but managed to escape it. 

The one with most impact was score_func and loss_func from sklearn.metrics.scorer.check_scoring, which was still used in quite a few different places, e.g. cross_validation.py, grid_search.py, a few different tests, ...
To be completely honest, I think the main reason I kept them originally was because it made the deprecated code removal slightly more straightforward.

* copy_Gram is used below in a function with positional arguments style so the only reason to keep it would be for self-documentating purposes ... I guess using named arguments passing-style is preferrable
* copy_X is used twice below, although replacing both occurences by True is probably fine
* Xy is not used and could definitely go