Increase maximum wholesale benefit

[zolanaj]

Citing a previous observation by @adfarth:

https://reopt.nrel.gov/tool/results/cb9b426f-242a-40d0-965a-09ea843e4105

In this scenario, the WHL is extremely high AND a NEM limit is set. However, REopt still sizes the system under the the NEM limit kW, but compensates the exports at the WHL rate. I had expected REopt to just size the system infinitely large, as it would be more profitable to blow past the NEM limit.

The underlying cause is a relatively small maximum wholesale benefit in place here. It may be worth increasing this so that the optimal size is much than the current limit; for now the proposed fix is that a user is warned if the wholesale limit is met (see #383).