Inline formatting consistency in docs

[kurbansitterley]

The docs are all over the place with regards to how we do inline formatting of:

• functions (e.g., calculate_scaling_factors)
• methods
• code (e.g., m.fs.costing)
• directories (e.g., data/technoeconomic)
• components/phases (e.g., Liq, TDS, H2O)
• variable names and classes (e.g., volume_liquid, FlowsheetBlock)

in some places we use monospaced_text, in others it is italics or bold, and sometimes we_use_no_formatting_at_all.

I don't think any of these are necessarily wrong or right, but we should be consistent.