Feature/objective function weighted sum#840

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minhki95 wants to merge 3 commits intooemof:devfrom minhki95:feature/objective_function_weighted_sum

+48-15

Commits on Apr 27, 2022

Add attribute cellular_system to enable cellular nested models
minhki95
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Enable weighted objective function with accordance to cellular system
minhki95
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Commits on May 2, 2022

Modify objective expression of investment flows for weighted sum approach
minhki95
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