Storage periodic boundaries for level

[PaulTalbot-INL]

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Pull Request Description

What issue does this change request address?

Closes #87.

What are the significant changes in functionality due to this change request?

By default (opt-out available), requires that a storage's final level in an evaluation window be equal to the initial level. While this removes a degree of freedom from optimal dispatch, it also removes the possibility of "free energy" or "free sink" because of boundary condition assumptions.

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For Change Control Board: Change Request Review

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• 4. Automated Tests should pass.
• 5. If significant functionality is added, there must be tests added to check this. Tests should cover all possible options. Multiple short tests are preferred over one large tes.
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• 8. If an analytic test is changed/added, the the analytic documentation must be updated/added.
• 9. If any test used as a basis for documentation examples have been changed, the associated documentation must be reviewed and assured the text matches the example.

[PaulTalbot-INL]

Note that we should post this to the discussion board, as it changes default behavior.

[PaulTalbot-INL]

Note in the original version of this problem, without the periodic level boundary constraint, the steam would fill the storage until the end of the analysis window. Now, since it has to return to original storage level, there's nowhere for the excess steam to go when the "steamer" is size 100, so I added this component as a low-cost steam sink.

[dylanjm]

Changes LGTM. This new capability will serve as a good default that's easy to explain and I guess could be considered "more realistic."

[dylanjm]

@mgarrouste Here is the PR implementing periodic boundary conditions for storage.