compute idealized regulatory costs by forecast year

[rjhanes]

regarding my review of idealized NPV and idealized internal NPV, the equations are fine except that it approximates idealized regulatory costs by an analytic integration to compute their present value. For uniformity of approach, we could replace that analytic integration with the expected costs by forecast year, which would mean we'd have to add the [forecast year] subscript to idealized regulatory costs, but this will make almost no difference numerically. Instead, I'm renaming idealized regulatory costs to idealized regulatory cost PV, to make the approach clearer.

[rjhanes]

closed in branch bwbreview and transferred into integratesubmodels