Remove 0-th network from restoration

[noahrhodes]

The restoration problems should return multi-networks ["1"]-["repair_periods"] rather than ["0"]-["repair_periods"]. If an initial operating point before any components are restored, a user can calculate that themselves.

This will require changes to iterative_restoration, replicate_restoration_network, and updates to most of the tests objective functions.

[noahrhodes]

A potential issue is for continually increasing load. If the "0" period is not included, then the first repair could be less load delivery that the network had before repairs begin.

(this is especially an issue for the iterative-restoration problem, but should likely be an additional processing step for that algorithm).