lisa.energy_model: Turn EnergyModel.capacity_scale into instance attribute
lisa.energy_model: Turn EnergyModel.capacity_scale into instance attribute

Turn EnergyModel.capacity_scale into an instance attribute since it was
modified by EnergyModel.__init__. Global constants exposed to the rest
of the code must not be modified after import time.

credp/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa