more control/visibility over the list of watchers for an issue

User problem:

"Often a random person will read a Mira issue that I logged and ask questions via comments. If I know that that person is watching the issue, then I only need to update the issue with my comments. If I don't know, then I will also need to forward the comment via email to that person".

Possible solutions:

• make the list of the watchers viewable;
• add oneself to the list of watchers whenever one comments on an issue
• "copy author and all commenters" checkbox when commenting