Launch Scrum Poker sessions for all issues of a Sprint

[codescape]

Add the ability to start Scrum Poker sessions for a previously selected set of issues. When one session is finished lead participants to the next Scrum Poker session.

Idea extracted from #59:

How to launch a session for all issues of a Sprint ?
As a Product Owner, I put stories from my backlog to the next sprint in my JIRA Board. I would like to launch a poker planning session for all issues in my next sprint with only one click. For now , I need to launch a poker planning session for all stories one by one.

[nevil]

This would be a very useful feature!
We have many issues per sprint so it would be very convenient to create sessions for all issues that belongs to a sprint.