Remove Discuss button from Insight and Resource objects

[tschaffter]

@ychae and I decided this morning to remove the Discuss button from the page of individual Resources and Insights to limit the number of places where users need to go to keep track of messages. Users are expected to discuss at the project level.

In the future, users will be able to "reference" Entities during the discussion (see #442).

[tschaffter]

@ychae Do you confirm this?

[tschaffter]

See #378 (comment).