Ability to reference an upgrade in sys.upgrades with it's sn.

[jckirton]

It seems that there is no way to reference an individual upgrade in sys.upgrades using the upgrade's sn, meaning you have to get sys.upgrades {full:true} and filter it in code.

This seems really strange and is somewhat annoying when you can't use the upgrade's index and don't want to filter through all the upgrades.