fixed bug that replaced all lumped elements in simulations, when using TerminalComponentModeler

[dmarek-flex]

Just had to copy any existing lumped elements before adding loads from the ports.

[tylerflex]

Ah yea, this can be a tricky one. I often wonder if some kind of append: bool argument to updated_copy() might be useful for some things. For example, it would be a shortcut to doing list(self.field) + list(new_things). maybe some other time.