Comment 1 for bug 1566684

I fear this might break forward compatibility for charms that still have upgrade-charm and config-changed hooks. Could this be amended to have the following logic instead?

Juju 2.0 Upgrade sequence:
 - Look for upgrade hook, if fail
 - Look for upgrade-charm, if fail
 - Skip

Juju 2.0 Configure sequence:
 - Look for config hook, if fail
 - Look for config-changed, if fail
 - Skip

This way charms developed with <=1.25 will still work in 2.0 since we don't have a max-juju-version field

Also, nitpick, since we're renaming things, `configure` seems more complete than `config` but that's just the color of the shed I'd prefer.