Make SrlBert model use SrlEvalMetric (#3168)
Make SrlBert model use SrlEvalMetric (#3168)

* Switch SemanticRoleLabeler metric to SrlEvalScorer.

* Switch back to https links, per f9e2029

* Add ignore_classes to SrlEvalScorer and ignore V in SRL model

* Enable specifying path to srl-eval.pl

* Only run span metric if it is enabled, and during evaluation

* Add comment explaining ignore_classes

* Add doc for srl_util

* Add srl_util.rst to allennlp.models.rst

* Fix position of comment

* Use SrlEvalMetric in SrlBert

allenai/allennlp,allenai/allennlp,allenai/allennlp,allenai/allennlp