Consider folder reorganization for AMO flowsheets

[adam-a-a]

We should consider reorganizing our folder structure for AMO related flowsheets to something that will be clearer when we incorporate flowsheets with detailed models. So far, we only have flowsheets based on zero-order models. Once we add in flowsheets that use more detailed models like ASM1, ASM2D, and ADM1, we'll want users (and developers) to be able to clearly distinguish between the simple (predominantly zero-order) and detailed examples.

Existing structure:
watertap/examples/flowsheets/case_studies/wastewater_resource_recovery

Suggested structure:
watertap/examples/flowsheets/case_studies/wastewater_resource_recovery\zero_order

watertap/examples/flowsheets/case_studies/wastewater_resource_recovery\detailed

[andrewlee94]

We also need to consider what is a case_study and what is not (and if we even want to make that distinction). There also appear to be some csv files lingering from the WT3 merger that should be cleaned up.