Merge branch 'add_comment_when_it_is_new' into 'master'

Check if comment exists before sending a reference to Jira

Currently every time an issue is mentioned, Jira service sends a reference to Jira.
To prevent problems like described in #265 , add another query to the process to retrieve all comments for the issue so we can see if it contains the reference we want to add.

See merge request !377