Bulk priority reshuffle

For our usage of Jira, we need a way to allow customers and managers to quickly view a list issues and reprioritise the stories by promoting/demoting their position in the list.

This is a procedure done in bulk (typically reshuffling the priority of about 20 items at a time) and therefore has to be fast and easy to use.

Currently it is causing a problem because it is too time consuming to go into each issue and edit it, and priorities are rated on a fixed scale (trival->blocker) rather than relative to other issues.