Add ability to prevent duplicates

[jmrodri]

Add the ability to have clone look for jira issues that have [UPSTREAM] in the Summary and possibly the issue number. Something like "give me jira issue with Summary that starts with [UPSTREAM and ends with #1234" That should return either nil or issue #1234.

Not sure yet what we do if we find one. First, option is do just log that we already found one.
I could see it "updating" the existing issue with the new contents of the github. OR possibly adding a new comment to the jira issue that contains comments from the github issue.