Add molar flows for precipitate and reagent to simplify reaktoro integration

[avdudchenko]

Fixes/Resolves:

N/A
(replace this with the issue # fixed or resolved, if no issue exists then a brief statement of what this PR does)

Summary/Motivation:

Adds molar flows of reagents and precipitates to simplify integration with reaktoro.

Changes proposed in this PR:

• adds flow_mol_precipitate and flow_mol_reagent as vars
• minor updates to scaling and cofing

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[ksbeattie]

@OOAmusat @zacharybinger can you review?

[OOAmusat]

This looks fine to me.