Support emitting analytical events from xblocks running in the LMS

XBlocks can and should use the "publish" method provided by the runtime to emit analytical events. In theory we could now start replacing calls to track_function with calls to publish, however, that migration is not handled by this change.

Fixes: AN-789
temporarily remove SR on capa alerts to fix problem submissions (LMS-2474)
Remove unused methods from comment_client
Remove unused *args and **kwargs from perform_request
Use requests library utility method for getting json results
Add more tags to comment_client request metrics

This captures real-time metrics for all of the comment client actions,
segregated by course_id, as well as other small-cardinality fields.

The goal is to be able to detect changes in forum usage, with the goal
of alerting on potential error conditions.
Merge pull request #3105 from edx/adam/hotifx-js

temporarily remove SR on capa alerts to fix problem submissions (LMS-247...
Merge pull request #3089 from mulby/gabe/publish

Support emitting analytical events from xblocks running in the LMS
this will allow for clientside javascript reporting
Merge pull request #3109 from edx/jarv/upgrade-newrelic-agent

this will allow for clientside javascript reporting
Add datadog metrics logging for django model creates, updates, and deletes
Skip video test that is failing in master
Merge pull request #3111 from edx/zoldak/skip-failing-tests

Skip video test that is failing in master
Temporarily disable the bok-choy test that is intermittenly failing
Merge remote-tracking branch 'origin/release' into adam/merge-release-2
AN-167 New chapter on role & skills of data czar and research team
Merge pull request #3038 from edx/ahodges/documentation/dataczar

AN-167 New chapter on role & skills of data czar and research team
Merge pull request #3112 from edx/zoldak/skip-failing-tests

Temporarily disable the bok-choy test that is intermittently failing
Merge pull request #3113 from edx/adam/merge-release-2

Adam/merge release 2
Custom JavaScript Display and Grading

DOC-105