include smart help text on node edit form #2290

#2290 

**DO NOT MERGE YET**

Commit 6160fcf updates the names of comment_sources sources to match the new spec (standardizes capitalization and renames "Drupal" to "Private" comments). It also standardizes the way the 4 different settings appear in the node edit form, including "smart" help text to inform users of the new policy (links users to update app settings if they want to enable/disable/change comment source).

Changes here are a work in progress until the comment_sources module tests pass.