Feature Request: Connect PRs to Issues

A really powerful feature of Waffle is the ability to display PRs in the board and connect PRs to Issues. https://github.com/waffleio/waffle.io/wiki/FAQs#prs-and-issues

It enables the workflow they describe here https://github.com/waffleio/waffle.io/wiki/Recommended-Workflow-Using-Pull-Requests-&-Automatic-Work-Tracking which is very neat.

Added KB[stage][1][Analysis] label

Milestone changed to %1.7.1

moved issue from Backlog to Analysis