Alternative to D22882.
Our use of "capacity" to refer to how much of a battery's original capacity remains is
confusing. This is made less confusing by inverting the number and referring to it as
"degradation". "Degradation: 21%" communicates that the battery has lost 21% of its
original capacity far better than "Capacity: 79%" does, because the latter is easily
confused with the battery's current charge level.
To further reduce the confusion, the battery's degradation lavel is relocated to the
{nav Battery} section.