Deprecation/Removal: Custom Datadog support, DEPR-9

[Michael Terry]

Hi there,

We plan to deprecate and remove specialized bulit-in support for the Datadog monitoring service in edx-platform. We are targeting removal after 2018-12-20.

Please read https://openedx.atlassian.net/browse/DEPR-9 for more information and to post any questions/comments. The proposed deadline for comments before acceptance is 2018-12-13.

Thanks, Michael Terry