Customizable default priority for issue reporting

As a great man once said:

It would be very useful to have an option to set the default value for priority the same way you set default values for components, milestones and versions.

But that got closed because we didn't whinge enough and there's no way to re-open it so I'm recreating it.

And yes, I ironically left the priority as major, even though it probably should be a minor thing.

<3