Jira control features in the bot

This set of changes allows the bot to authenticate as multiple users using their tokens. When granted with a token, the bot can comment on and resolve issues in the name of the requesting user, thus the change is indistinguishable from one made by the user from the web interface.

This set of changes still has some security issues, i.e. it allows a user to use pre-committed token based on having the same user ident, and user ident can be faked. This works in my environment (is secure, as the server enforces user ident based on IRC client authentication), so I am not going to pursue fixing this.