Add support for comment types and comments.

Problem/Motivation

add abillity to notify about comments, please.

I'd like to use that module for a forum like community build on top of Drupal. Big pat of that should be the forum module and so i'd like it íf this module will be able in the futher not only to notify about nodes, but about comments of a particular comment type.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes