update sparse_encoder if statements to type rather than name

added tfidf encoder, edited hybrid layer to let user choose sparse encoder type

These now match the number of non-other types.

Threshold checks done outside of _semantic_classify.

Testing more efficient as not using dl._query() accross every threshold.

Test cases aren't just the original Decision utterances now, but semantically similar utterances.

Also added new max_score_in_top_class method, which chooses the top score of the top scoring vector in the top class to compare to the threshold value.