[MRG+1] PR for model_evaluation.rst changes to fix issue #3661, "Document negation of loss as scoring parameter"

* doc/modules/model_evaluation.rst in the MattpSoftware fork contains my changes for issue #3661.

* issue-3661/model_evaluation_copy_edited.rst also fixes typos I found when reading the document.

* issue-3661/model_evaluation_edit_notes.txt has the explanation for the changes in model_evaluation_copy_edited.rst, and flags a few other other items for questions.
Why reiterate that it's caused by setting to an unknown value.

The point is that the log loss issue is a note about a particular scorer. Maybe you're better off placing a note in the table above that `log_loss` requires `predict_proba` support. (After all, there may be implementations outside of sklearn that also require explicit probability estimation flags, not just `SVC`.)